# Geominerals/Oxidanes

Oxidane minerals contain more than 25 molecular % H$_2$O.
The most common oxidane on the surface of the Earth is the liquid known as water. It occurs in the atmosphere as water vapor, and as a mineral usually referred to as ice.

## Water of crystallization

Water of crystallization or water of hydration is water molecules that are present inside crystals. Water is often incorporated in the formation of crystals from aqueous solutions. In some contexts, water of crystallization is the total mass of water in a substance at a given temperature and is mostly present in a definite (stoichiometric) ratio. Classically, "water of crystallization" refers to water that is found in the crystal structure, or crystalline framework of a metal complex or a salt, which is not directly bonded to the metal cation.
Mostly, the term is limited to non-coordinated interstitial water.
Coordination complex, or coordinated water, is directly bonded to a central atom on a lattice point.
Anion water has hydrogen bonds to anions.
Lattice water has no direct bonding with an ion.
Constitution water is water present as hydroxyl groups.
Zeolite water is water that occupies vacancies of a crystal; i.e., empty sites in the crystal lattice and may be removed without changing the crystal structure.
Upon crystallization from water, or water-containing solvents, many compounds incorporate water molecules in their crystalline frameworks. Water of crystallization can generally be removed by heating a sample but the crystalline properties are often lost. For example, in the case of sodium chloride, the dihydrate is unstable at room temperature.
Coordination sphere of Na$^+$ in the metastable dihydrate of sodium chloride is shown in the figure on the right.
The image on the left shows hydrogen bonding. This metal aquo complex crystallizes with water of hydration, which interacts with the sulfate and with the [Fe(H$_2$O)$_6$]$^{2+}$ centers.
A salt with associated water of crystallization is known as a hydrate. The structure of hydrates can be quite elaborate, because of the existence of hydrogen bonds that define polymeric structures.
Historically, the structures of many hydrates were unknown, and the dot in the formula of a hydrate was employed to specify the composition without indicating how the water is bound. Examples:
* CuSO$_4$•5H $_2$O - copper(II) sulfate pentahydrate
* CoCl$_2$•6H $_2$O - cobalt(II) chloride hexahydrate
* SnCl$_2$•2H $_2$O - tin(II) (or stannous) chloride dihydrate.
For many salts, the exact bonding of the water is unimportant because the water molecules are made labile upon dissolution. For example, an aqueous solution prepared from CuSO$_4$•5H $_2$O and anhydrous CuSO$_4$ behave identically. Therefore, knowledge of the degree of hydration is important only for determining the equivalent weight: one mole of CuSO$_4$•5H $_2$O weighs more than one mole of CuSO$_4$. In some cases, the degree of hydration can be critical to the resulting chemical properties. For example, anhydrous rhodium(III) chloride, RhCl$_3$ is not soluble in water and is relatively useless in organometallic chemistry whereas RhCl$_3$•3H $_2$O is versatile. Similarly, hydrated AlCl$_3$ is a poor Lewis acid and thus inactive as a catalyst for Friedel-Crafts reactions. Samples of AlCl$_3$ must therefore be protected from atmospheric moisture to preclude the formation of hydrates.
Three water ligands are terminal, three bridge. Two aspects of metal aquo complexes are illustrated: the high coordination number typical for Ca$^{2+}$ and the role of water as a bridging ligand.
Crystals of hydrated copper(II) sulfate consist of [Cu(H$_2$O)$_4$]$^{2+}$ centers linked to SO$_4$$^{2−}$ ions. Copper is surrounded by six oxygen atoms, provided by two different sulfate groups and four molecules of water. A fifth water resides elsewhere in the framework but does not bind directly to copper. The cobalt chloride mentioned above occurs as [Co(H$_2$O)$_6$]$^{2+}$ and Cl$^−$. In tin chloride, each Sn(II) center is pyramidal (mean O/Cl-Sn-O/Cl angle is 83°) being bound to two chloride ions and one water. The second water in the formula unit is hydrogen-bonded to the chloride and to the coordinated water molecule. Water of crystallization is stabilized by electrostatic attractions, consequently hydrates are common for salts that contain +2 and +3 cations as well as −2 anions. In some cases, the majority of the weight of a compound arises from water. Glauber's salt, Na$_2$SO$_4$(H$_2$O)$_{10}$, is a white crystalline solid with greater than 50% water by weight.
Consider the case of nickel(II) chloride hexahydrate. This species has the formula NiCl$_2$(H$_2$O)$_6$. Crystallographic analysis reveals that the solid consists of [trans-NiCl$_2$(H$_2$O)$_4$] subunits that are hydrogen bonded to each other as well as two additional molecules of H$_2$O. Thus 1/3 of the water molecules in the crystal are not directly bonded to Ni$^{2+}$, and these might be termed "water of crystallization".
The water content of most compounds can be determined with a knowledge of its formula. An unknown sample can be determined through thermogravimetric analysis (TGA) where the sample is heated strongly, and the accurate weight of a sample is plotted against the temperature. The amount of water driven off is then divided by the molar mass of water to obtain the number of molecules of water bound to the salt.
Water is particularly common solvent to be found in crystals because it is small and polar. But all solvents can be found in some host crystals. Water is noteworthy because it is reactive, whereas other solvents such as benzene are considered to be chemically innocuous. Occasionally more than one solvent is found in a crystal, and often the stoichiometry is variable, reflected in the crystallographic concept of "partial occupancy." It is common and conventional for a chemist to "dry" a sample with a combination of vacuum and heat "to constant weight."
For other solvents of crystallization, analysis is conveniently accomplished by dissolving the sample in a deuterated solvent and analyzing the sample for solvent signals by NMR spectroscopy. Single crystal X-ray crystallography is often able to detect the presence of these solvents of crystallization as well. Other methods may be currently available.

## Table of crystallization water in some inorganic halides

In the table below are indicated the number of molecules of water per metal (M) in various salts.
| Formula of hydrated metal halides | Coordination sphere of the metal | Equivalents of water of crystallization that are not bound to M | Remarks |
| (Calcium chloride) CaCl$_2$(H$_2$O)$_6$ | [Ca(μ-H$_2$O)$_6$(H$_2$O)$_3$]$^{2+}$ | none | example of water as a bridging ligand |
| (Titanium(III) chloride) TiCl$_3$(H$_2$O)$_6$ | trans-[TiCl$_2$(H$_2$O)$_4$]$^+$ | two | isomorphous with VCl$_3$(H$_2$O)$_6$ |
| (Vanadium(III) chloride) VCl$_3$(H$_2$O)$_6$ | trans-[VCl$_2$(H$_2$O)$_4$]$^+$ | two | |
| (Vanadium(III) bromide) VBr$_3$(H$_2$O)$_6$ | trans-[VBr$_2$(H$_2$O)$_4$]$^+$ | two | |
| (Vanadium(III) iodide) VI$_3$(H$_2$O)$_6$ | [V(H$_2$O)$_6$]$^{3+}$ | none | relative to Cl$^−$ and Br$^−$,I$^−$ competes poorly with water as a ligand for V(III) |
| Nb$_6$Cl$_{14}$(H$_2$O)$_8$ | [Nb$_6$Cl$_{14}$(H$_2$O)$_2$] | four | |
| (Chromium(III) chloride) CrCl$_3$(H$_2$O)$_6$ | trans-[CrCl$_2$(H$_2$O)$_4$]$^+$ | two | dark green isomer, aka "Bjerrums's salt" |
| (Chromium(III) chloride) CrCl$_3$(H$_2$O)$_6$ | [CrCl(H$_2$O)$_5$]$^{2+}$ | one | blue-green isomer |
| (Chromium(II) chloride) CrCl$_2$(H$_2$O)$_4$ | trans-[CrCl$_2$(H$_2$O)$_4$] | none | square planar/tetragonal distortion |
| (Chromium(III) chloride) CrCl$_3$(H$_2$O)$_6$ | [Cr(H$_2$O)$_6$]$^{3+}$ | none | violet isomer. isostructural with aluminium compound |
| (Aluminium trichloride#Hydrate) AlCl$_3$(H$_2$O)$_6$ | [Al(H$_2$O)$_6$]$^{3+}$ | none | isostructural with the Cr(III) compound |
| (Manganese(II) chloride) MnCl$_2$(H$_2$O)$_6$ | trans-[MnCl$_2$(H$_2$O)$_4$] | two | |
| (Manganese(II) chloride) MnCl$_2$(H$_2$O)$_4$ | cis-[MnCl$_2$(H$_2$O)$_4$] | none | cis molecular, the unstable trans isomer has also been detected |
| (Manganese(II) bromide) MnBr$_2$(H$_2$O)$_4$ | cis-[MnBr$_2$(H$_2$O)$_4$] | none | cis, molecular |
| (Manganese(II) chloride) MnCl$_2$(H$_2$O)$_2$ | trans-[MnCl$_4$(H$_2$O)$_2$] | none | polymeric with bridging chloride |
| (Manganese(II) bromide) MnBr$_2$(H$_2$O)$_2$ | trans-[MnBr$_4$(H$_2$O)$_2$] | none | polymeric with bridging bromide |
| (Iron(II) chloride) FeCl$_2$(H$_2$O)$_6$ | trans-[FeCl$_2$(H$_2$O)$_4$] | two | |
| (Iron(II) chloride) FeCl$_2$(H$_2$O)$_4$ | trans-[FeCl$_2$(H$_2$O)$_4$] | none | molecular |
| (Iron(II) bromide) FeBr$_2$(H$_2$O)$_4$ | trans-[FeBr$_2$(H$_2$O)$_4$] | none | molecular |
| (Iron(II) chloride) FeCl$_2$(H$_2$O)$_2$ | trans-[FeCl$_4$(H$_2$O)$_2$] | none | polymeric with bridging chloride |
| (Iron(III) chloride) FeCl$_3$(H$_2$O)$_6$ | trans-[FeCl$_2$(H$_2$O)$_4$]$^+$ | two | one of four hydrates of (ferric chloride, isostructural with Cr analogue |
| (Iron(III) chloride) FeCl$_3$(H$_2$O)$_{2.5}$ | cis-[FeCl$_2$(H$_2$O)$_4$]$^+$ | two | the dihydrate has a similar structure, both contain FeCl$_4$$^−$ anions. |
| (Cobalt(II) chloride) CoCl$_2$(H$_2$O)$_6$ | trans-[CoCl$_2$(H$_2$O)$_4$] | two | |
| (Cobalt(II) bromide) CoBr$_2$(H$_2$O)$_6$ | trans-[CoBr$_2$(H$_2$O)$_4$] | two | |
| (Cobalt(II) iodide) CoI$_2$(H$_2$O)$_6$ | [Co(H$_2$O)$_6$]$^{2+}$ | none | iodide competes poorly with water |
| (Cobalt(II) bromide) CoBr$_2$(H$_2$O)$_4$ | trans-[CoBr$_2$(H$_2$O)$_4$] | none | molecular |
| (Cobalt(II) chloride) CoCl$_2$(H$_2$O)$_4$ | cis-[CoCl$_2$(H$_2$O)$_4$] | none | note: cis molecular |
| (Cobalt(II) chloride) CoCl$_2$(H$_2$O)$_2$ | trans-[CoCl$_4$(H$_2$O)$_2$] | none | polymeric with bridging chloride |
| (Cobalt(II) chloride) CoBr$_2$(H$_2$O)$_2$ | trans-[CoBr$_4$(H$_2$O)$_2$] | none | polymeric with bridging bromide |
| (Nickel(II) chloride) NiCl$_2$(H$_2$O)$_6$ | trans-[NiCl$_2$(H$_2$O)$_4$] | two | |
| (Nickel(II) chloride) NiCl$_2$(H$_2$O)$_4$ | cis-[NiCl$_2$(H$_2$O)$_4$] | none | note: cis molecular |
| (Nickel(II) bromide) NiBr$_2$(H$_2$O)$_6$ | trans-[NiBr$_2$(H$_2$O)$_4$] | two | |
| (Nickel(II) iodide) NiI$_2$(H$_2$O)$_6$ | [Ni(H$_2$O)$_6$]$^{2+}$ | none | iodide competes poorly with water |
| (Nickel(II) chloride) NiCl$_2$(H$_2$O)$_2$ | trans-[NiCl$_4$(H$_2$O)$_2$] | none | polymeric with bridging chloride |
| (Copper(II) chloride) CuCl$_2$(H$_2$O)$_2$ | [CuCl$_4$(H$_2$O)$_2$]$_2$ | none | tetragonally distorted two long Cu-Cl distances |
| (Copper(II) bromide) CuBr$_2$(H$_2$O)$_4$ | [CuBr$_4$(H$_2$O)$_2$]$_n$ | two | tetragonally distorted two long Cu-Br distances |
| (Zinc(II) chloride) ZnCl$_2$(H$_2$O)$_{1.33}$ | 2 ZnCl$_2$ + ZnCl$_2$(H$_2$O)$_4$ | none | coordination polymer with both tetrahedral and octahedral Zn centers |
| (Zinc(II) chloride) ZnCl$_2$(H$_2$O)$_{2.5}$ | Cl$_3$Zn(μ-Cl)Zn(H$_2$O)$_5$ | none | tetrahedral and octahedral Zn centers |
| (Zinc(II) chloride) ZnCl$_2$(H$_2$O)$_3$ | [ZnCl$_4$]$^{2-}$ + Zn(H$_2$O)$_6$]$^{2+}$ | none | tetrahedral and octahedral Zn centers |
| (Zinc(II) chloride) ZnCl$_2$(H$_2$O)$_{4.5}$ | [ZnCl$_4$]$^{2-}$ + [Zn(H$_2$O)$_6$]$^{2+}$ | three | tetrahedral and octahedral Zn centers |

## Hydrates of metal sulfates

Transition metal sulfates form a variety of hydrates, each of which crystallizes in only one form. The sulfate group often binds to the metal (M), especially for those salts with fewer than six aquo ligands. The heptahydrates, which are often the most common salts, crystallize as monoclinic and the less common orthorhombic forms. In the heptahydrates, one water is in the lattice and the other six are coordinated to the ferrous center. Many of the metal sulfates occur in nature, being the result of weathering of mineral sulfides. Many monohydraes are known.
| Formula of hydrated metal ion sulfate | Coordination sphere of the metal ion | Equivalents of water of crystallization that are not bound to M | mineral name | Remarks |
| (Magnesium sulfate) MgSO$_4$(H$_2$O)$_4$ | [Mg(H$_2$O)$_4$(κ',κ$^1$-SO$_4$)]$_2$ | none | | sulfate is bridging ligand, 8-membered Mg$_2$O$_4$S$_2$ rings |
| (Magnesium sulfate) MgSO$_4$(H$_2$O)$_6$ | [Mg(H$_2$O)$_6$] | none | hexahydrite | common motif |
| (Magnesium sulfate) MgSO$_4$(H$_2$O)$_7$ | [Mg(H$_2$O)$_6$] | one | epsomite | common motif |
| (Titanyl sulfate) TiOSO$_4$(H$_2$O) | [Ti(μ-O)$_2$(H$_2$O)(κ$^1$-SO$_4$)$_3$] | none | | further hydration gives gels |
| (Vanadium(II) sulfate) VSO$_4$(H$_2$O)$_6$ | [V(H$_2$O)$_6$] | none | | Adopts the hexahydrite motif |
| (Vanadyl sulfate) VOSO$_4$(H$_2$O)$_5$ | [VO(H$_2$O)$_4$(κ$^1$-SO$_4$)$_4$] | one | | |
| (Chromium(III) sulfate) Cr$_2$(SO$_4$)$_3$(H$_2$O)$_{18}$ | [Cr(H$_2$O)$_6$] | six | | One of several chromium(III) sulfates |
| (Manganese(II) sulfate) MnSO$_4$(H$_2$O) | [Mn(μ-H$_2$O)$_2$(κ$^1$-SO$_4$)$_4$] | none | | The most common of several hydrated manganese(II) sulfates |
| (Manganese(II) sulfate) MnSO$_4$(H$_2$O)$_7$ | [Mn(H$_2$O)$_6$] | one | mallardite | see Mg analogue |
| (Iron(II) sulfate) FeSO$_4$(H$_2$O)$_7$ | [Fe(H$_2$O)$_6$] | one | melanterite | see Mg analogue |
| (Iron(II) sulfate) FeSO$_4$(H$_2$O)$_4$ | [Fe(H$_2$O)$_4$(κ',κ$^1$-SO$_4$)]$_2$ | none | | sulfate is bridging ligand, 8-membered Fe$_2$O$_4$S$_2$ rings |
| Fe$^{II}$(Fe$^{III}$)$_2$(SO$_4$)$_4$(H$_2$O)$_{14}$ | [Fe$^{II}$(H$_2$O)$_6$]$^{2+}$[Fe$^{III}$(H$_2$O)$_4$(κ$^1$-SO$_4$)$_2$]$^−$$_2$ | none | | sulfates are terminal ligands on Fe(III) |
| (Cobalt(II) sulfate) CoSO$_4$(H$_2$O)$_7$ | [Co(H$_2$O)$_6$] | one | | see Mg analogue |
| (Cobalt(II) sulfate) CoSO$_4$(H$_2$O)$_6$ | [Co(H$_2$O)$_6$] | none | morehouseite | see Mg analogue |
| (Cobalt(II) sulfate) CoSO$_4$(H$_2$O)$_7$ | [Co(H$_2$O)$_6$] | one | bieberite | see Fe analogue |
| (Nickel(II) sulfate) NiSO$_4$(H$_2$O)$_6$ | [Ni(H$_2$O)$_6$] | none | retgersite | One of several nickel sulfate hydrates |
| (Nickel(II) sulfate) NiSO$_4$(H$_2$O)$_7$ | [Ni(H$_2$O)$_6$] | | morenosite | |
| (Copper(II) sulfate) CuSO$_4$(H$_2$O)$_5$ | [Cu(H$_2$O)$_4$(κ$^1$-SO$_4$)$_2$] | one | chalcantite | sulfate is bridging ligand |
| (Copper(II) sulfate) CuSO$_4$(H$_2$O)$_7$ | [Cu(H$_2$O)$_6$] | one | boothite | |
| (Zinc sulfate) ZnSO$_4$(H$_2$O)$_4$ | [Zn(H$_2$O)$_4$(κ',κ$^1$-SO$_4$)]$_2$ | none | | sulfate is bridging ligand, 8-membered Zn$_2$O$_4$S$_2$ ringss |
| (Zinc sulfate) ZnSO$_4$(H$_2$O)$_6$ | [Zn(H$_2$O)$_6$] | none | | see Mg analogue |
| (Zinc sulfate) ZnSO$_4$(H$_2$O)$_7$ | [Zn(H$_2$O)$_6$] | one goslarite | | see Mg analogue |
| (Cadmium sulfate) CdSO$_4$(H$_2$O) | [Cd(μ-H$_2$O)$_2$(κ$^1$-SO$_4$)$_4$] | none | | bridging water ligand |

## Hydrates of metal nitrates

Transition metal nitrates form a variety of hydrates. The nitrate anion often binds to the metal (M), especially for those salts with fewer than six aquo ligands.
| Formula of hydrated metal ion nitrate | Coordination sphere of the metal ion | Equivalents of water of crystallization that are not bound to M | Remarks |
| (Chromium(III) nitrate) Cr(NO$_3$)$_3$(H$_2$O)$_6$ | [Cr(H$_2$O)$_6$]($^{3+}$ | three | octahedral configuration isostructural with Fe(NO$_3$)$_3$(H$_2$O)$_9$ |
| (Manganese(II) nitrate) Mn(NO$_3$)$_2$(H$_2$O)$_4$ | cis-[Mn(H$_2$O)$_4$(κ$^1$-ONO$_2$)$_2$] | none | octahedral configuration |
| (Manganese(II) nitrate) Mn(NO$_3$)$_2$(H$_2$O) | [Mn(H$_2$O)(μ-ONO$_2$)$_5$] | none | octahedral configuration |
| (Iron(III) nitrate) Fe(NO$_3$)$_3$(H$_2$O)$_9$ | [Fe(H$_2$O)$_6$]$^{3+}$ | three | octahedral configuration isostructural with Cr(NO$_3$)$_3$(H$_2$O)$_9$ |
| (Iron(III) nitrate) Fe(NO$_3$)$_3$)(H$_2$O)$_4$ | [Fe(H$_2$O)$_3$(κ$^2$-O$_2$NO)$_2$]$^+$ | one | pentagonal bipyramid |
| (Iron(III) nitrate) Fe(NO$_3$)$_3$(H$_2$O)$_5$ | [Fe(H$_2$O)$_5$(κ$^1$-ONO$_2$)]$^{2+}$ | none | octahedral configuration |
| (Iron(III) nitrate) Fe(NO$_3$)$_3$(H$_2$O)$_6$ | [Fe(H$_2$O)$_6$]$^{3+}$ | none | octahedral configuration |
| (Cobalt(II) nitrate) Co(NO$_3$)$_2$(H$_2$O)$_2$ | [Co(H$_2$O)$_2$(κ$^1$-ONO$_2$)$_2$] | none | octahedral configuration |
| (Cobalt(II) nitrate) Co(NO$_3$)$_2$(H$_2$O)$_4$ | [Co(H$_2$O)$_4$(κ$^1$-ONO$_2$)$_2$ | none | octahedral configuration |
| (Cobalt(II) nitrate) Co(NO$_3$)$_2$(H$_2$O)$_6$ | [Co(H$_2$O)$_6$]$^{2+}$ | none | octahedral configuration. |
| α-(Nickel(II) nitrate) Ni(NO$_3$)$_2$(H$_2$O)$_4$ | cis-[Ni(H$_2$O)$_4$(κ$^1$-ONO$_2$)$_2$] | none | octahedral configuration. |
| β-(Nickel(II) nitrate) Ni(NO$_3$)$_2$(H$_2$O)$_4$ | trans-[Ni(H$_2$O)$_4$(κ$^1$-ONO$_2$)$_2$] | none | octahedral configuration. |
| (Copper(II) nitrate) Cu(NO$_3$)$_2$(H$_2$O) | [Cu(H$_2$O)(κ$^2$-ONO$_2$)$_2$] | none | octahedral configuration. |
| (Copper(II) nitrate) Cu(NO$_3$)$_2$(H$_2$O)$_{1.5}$ | uncertain | uncertain | uncertain |
| (Copper(II) nitrate) Cu(NO$_3$)$_2$(H$_2$O)$_{2.5}$ | [Cu(H$_2$O)$_2$(κ$^1$-ONO$_2$)$_2$] | one | square planar |
| (Copper(II) nitrate) Cu(NO$_3$)$_2$(H$_2$O)$_3$ | uncertain | uncertain | uncertain |
| (Copper(II) nitrate) Cu(NO$_3$)$_2$(H$_2$O)$_6$ | [Cu(H$_2$O)$_6$]$^{2+}$ | none | octahedral configuration |
| (Zinc nitrate) Zn(NO$_3$)$_2$(H$_2$O)$_4$ | cis-[Zn(H$_2$O)$_4$(κ$^1$-ONO$_2$)$_2$] | none | octahedral configuration. |

## Ice cross sections

Def. any frozen "volatile chemical, such as water, ammonia, or carbon dioxide" is called an ice.

## Black ice cross sections

Black ice "growth rate is proportional to the rate at which energy is transferred from the bottom surface of the ice layer to the air above."
At the right is a vertical thin section through the black ice of the pond. It shows granular snow ice (top) and columnar black ice (bottom).

## Sea ice cross sections

At the right is a thin section of Antarctic sea ice. It was taken from an ice core.

## Ice core cross sections

At the left is a thin section of half an ice core from Antarctica.
"Thin sections were made in the field to examine crystal sizes and fabrics."
"The GRIP core offers a unique possibility to study the growth, rotation and recrystallization of polar ice at an ideal location, covering a time span of more than 100,000 years. This information is obtained by a comprehensive thin section study of crystal sizes and c-axis orientations along its entire length. The results confirm earlier, basic observations on deep ice cores and have led to new insights. A significant variation of crystal size with climatic parameters is shown to persist to a great depth in the core; the development of a strong crystalline anisotropy in the ice sheet is also demonstrated."

## Megacryometeors

A megacryometeor is a very large chunk of ice sometimes called huge hailstones, but do not need to form in thunderstorms.
A megacryometeor is a very large chunk of ice which, despite sharing many textural, hydro-chemical and isotopic features detected in large hailstones, is formed under unusual atmospheric conditions which clearly differ from those of the cumulonimbus cloud scenario (i.e. clear-sky conditions). They are sometimes called huge hailstones, but do not need to form in thunderstorms. Jesus Martinez-Frias, a planetary geologist at the Center for Astrobiology in Madrid, pioneered research into megacryometeors in January 2000 after ice chunks weighing up to 6.6 pounds (3.0 kg) rained on Spain out of cloudless skies for ten days.

## Hails

Def. "pieces of ice falling as precipitation" are called hail.
Def. "[a] single ball of hail" is called a hailstone.

## Sleet

Ice pellets (also referred to as sleet by the United States National Weather Service) are a form of precipitation consisting of small, translucent balls of ice. Ice pellets are usually smaller than hailstones and are different from graupel, which is made of rime, or rain and snow mixed, which is soft. Ice pellets often bounce when they hit the ground, and generally do not freeze into a solid mass unless mixed with freezing rain. The METAR code for ice pellets is PL.
Def. rain "which freezes before reaching the ground" is called sleet.
Def. "a single pellet of sleet" is called an ice pellet.

## Graupel

The METAR reporting code for hail 5 mm (0.20 in) or greater is GR, while smaller hailstones and graupel are coded GS. ... Hail has a diameter of 5 millimetres (0.20 in) or more. Hailstones can grow to 15 centimetres (6 in) and weigh more than 0.5 kilograms (1.1 lb).
Graupel ... also called soft hail or snow pellets refers to precipitation that forms when supercooled droplets of water are collected and freeze on a falling snowflake, forming a 2–5 mm (0.079–0.197 in) ball of rime.
Def. a "precipitation that forms when supercooled droplets of water condense on a snowflake" is called graupel.
Strictly speaking, graupel is not the same as hail or ice pellets, although it is sometimes referred to as small hail. However, the World Meteorological Organization defines small hail as snow pellets encapsulated by ice, a precipitation halfway between graupel and hail.
The frozen droplets on the surface of rimed crystals are hard to resolve and the topography of a graupel particle is not easy to record with a light microscope because of the limited resolution and depth of field in the instrument. However, observations of snow crystals with a low-temperature scanning electron microscope (LT-SEM) clearly show cloud droplets measuring up to 50 μm (0.00197 in) on the surface of the crystals. The rime has been observed on all four basic forms of snow crystals, including plates, dendrites, columns and needles. As the riming process continues, the mass of frozen, accumulated cloud droplets obscures the identity of the original snow crystal, thereby giving rise to a graupel particle.
Graupel commonly forms in high altitude climates and is both denser and more granular than ordinary snow, due to its rimed exterior. Macroscopically, graupel resembles small beads of polystyrene. The combination of density and low viscosity makes fresh layers of graupel unstable on slopes, and layers of 20–30 cm (7.9–11.8 in) present a high risk of dangerous slab avalanches. In addition, thinner layers of graupel falling at low temperatures can act as ball bearings below subsequent falls of more naturally stable snow, rendering them also liable to avalanche. Graupel tends to compact and stabilise ("weld") approximately one or two days after falling, depending on the temperature and the properties of the graupel.

## Snows

Def. water ice crystals falling as light white flakes are called snow.
White is the color of fresh milk and snow. It is the color the human eye sees when it looks at light which contains all the wavelengths of the visible spectrum, at full brightness and without absorption. It does not have any hue.

## Rimes

Def. "ice formed by the rapid freezing of cold water droplets of fog onto a cold surface" is called rime.
Hard rime is a white ice that forms when the water droplets in fog freeze to the outer surfaces of objects. It is often seen on trees atop mountains and ridges in winter, when low-hanging clouds cause freezing fog. This fog freezes to the windward (wind-facing) side of tree branches, buildings, or any other solid objects, usually with high wind velocities and air temperatures between −2 and −8 °C (28.4 and 17.6 °F).

## Blue ices

Blue ice occurs when snow falls on a glacier, is compressed, and becomes part of a glacier. Blue ice was observed in Tasman Glacier, New Zealand in January 2011. Ice is blue for the same reason water is blue: it is a result of an overtone of an oxygen-hydrogen (O-H) bond stretch in water which absorbs light at the red end of the visible spectrum.

## Black ices

Black ice (congelation ice) "forms as water freezes on the bottom of the ice cover and the latent heat of crystallization is conducted upwards through the ice and snow to the atmosphere."

## Congelation ices

"Congelation ice is often referred to as black ice because it has a high optical depth that permits significant light transmission to the underlying water."
The image on the right shows high optical depth and bubbles trapped and frozen under a thick layer of black ice.

## Icebergs

The first image on the right shows that when the polar sea is calm, the underside of icebergs can easily be observed in the clear waters of the Arctic Ocean.
Centered in the image second down on the right is a black ice growler from a recently calved iceberg closing in on the shore at the old heliport in Upernavik, Greenland. Such black ice growlers originate from glacial rifts, or crevasses, filled with melting water, which freezes into transparent ice without air bubbles.
On the left is an image of the surface texture on a black ice growler. There are bowl-like depressions in the surface created by the melting process of sea water.

## Ice tsunamis

"Along the shores of Lake Erie, the gusts were so strong that blocks of ice surged over the shoreline and formed walls as high as 30 feet—a striking phenomenon known as an "ice tsunami"."
"Ice tsunamis—also known as “ice shoves” and “ivu,” among other names—are rare, but well-documented events."
Ice "tsunamis were being studied as far back as 1822, when an American naturalist commented on “rocks, on level ground, taking up a gradual line of march [along a lakebed] and overcoming every obstacle in ... escaping the dominion of Neptune.”"
Ice "tsunamis tend to occur when three conditions are in place. The event is most common in springtime, when ice that covers large bodies of water starts to thaw, but has not yet melted. If strong winds then blow through the area, they can push the ice towards the water’s edge—and winds in the Lake Erie region were indeed quite powerful, reaching hurricane-like speeds of up to 74 miles per hour. The third condition is a gently sloping shoreline; the gentler the slope, the less resistance the ice meets as it piles up and pushes inland."
"The first slabs or sheets move on shore, creating a traffic jam, with ice piling on top and behind. With the buildup of ice, and the power behind it, it has the potential to damage anything in its path."

## Ice streams

On the right is a radarsat image of ice streams flowing into the Filchner-Ronne ice shelf. Annotations outline the Rutford ice stream.
Def. "a current of ice in an ice sheet or ice cap that flows faster than the surrounding ice" is called an ice stream.

## Ice wedging

A form of mechanical weathering, that is of/related to ice, is frost action (Alternate freezing and thawing of soil and rock). A famous type of frost action is the process of ice wedging.
Ice wedging starts when water seeps into the cracks [in the rocks] and, when the temperature drops to freezing temperatures, freezes. When it freezes, it also expands. The expanding ice pushes against the sides of the crack. This causes the crack to widen, and eventually (when repeated several and several times) breaks the rock apart.

## Ice sheets

Def. "a dome-shaped mass of glacier ice that covers surrounding terrain and is greater than 50,000 square kilometers (12 million acres)" is called an ice sheet.

## Glaciers

On the right is a radar image of Alfred Ernest Ice Shelf on Ellesmere Island, taken by the ERS-1 satellite.
Def. "a mass of ice that originates on land, usually having an area larger than one tenth of a square kilometer" is called a glacier.

## Surging glaciers

Def. "a glacier that experiences a dramatic increase in flow rate, 10 to 100 times faster than its normal rate; usually surge events last less than one year and occur periodically, between 15 and 100 years" is called a surging glacier.
"In 1941, Hole-in-the-Wall Glacier [imaged at the right] surged, also knocking over trees during its advance."
An "outlet glacier of the Sermersauq Ice Cap [on Disko Island, West Greenland, shown at the left with progressive surges marked] has surged 10.5 km downvalley to within 10 km of the fjord. [...] surging of the glacier, begun in 1995, was undetected until July 1999, when it was discovered during a geomorphic survey of the valley. Mapping from TM, Landsat and SPOT satellite imagery, and subsequent field work have documented the history of the event. On 17 June 1995 the terminus of the glacier was about where it appears in the 1985 air photography [...]. By 24 September 1995 the glacier had advanced 1.25 km and by 12 October another 1.25 km (mean advance during the second period : 70 m day$^{-1}$). The advance slowed from 18 m day$^{-1}$ in 1996 to 5 m day$^{-1}$ in 1997 and <1 m day$^{-1}$ between 1997 and 1999. By summer 1999 the advance ceased; the maximum extension of the terminus, about 10.5 km down-valley to about 10 km from the head of the fjord, was mapped from imagery on 9 July 1999 [...]."

## Astroglaciers

Astroglaciology is the observation and interpretation of glacial structures on rocky objects such as Ganymede from above.

## Liquid meteors

Liquid water precipitation falls from the atmosphere and reaches the ground, such as drizzle and rain. Suspended liquid water particles may form and remain suspended in the air (damp haze, cloud, fog, and mist), or may be lifted by the wind from the Earth’s surface (blowing spray) causing restrictions to visibility.

## Rains

Def. "condensed water falling from a cloud" is called rain.
Def. "the amount of rain that falls on a single occasion" is called a rainfall.

## Rivers

Def. a large and often winding stream which drains a land mass, carrying water down from higher areas to a lower point, ending at an ocean or in an inland sea is called a river.

## Meanders

Def. a winding, crooked, or involved course or a tortuous or intricate movement of water as a stream or river is called a meander.

## Rapids

Def. a rough section of a river or stream which is difficult to navigate due to the swift and turbulent motion of the water is called a rapid.
On the right are rapids featuring white water before the Rhine Falls.

## Waterfalls

Def. a flow of water over the edge of a cliff is called a waterfall.
Angel Falls in the image on the left is the world's tallest at 979 m.

## Meltwaters

"On a summit flight, we were able to see the source of the meltwater stream. It appears to starts to the right of the dome where a fall face can be seen and continues down."
The image on the left shows flooding some 7.6 m deep caused by the melting of Drift Glacier.

## Abernathyites

Abernathyite (IMA mineral symbol: Abn) is a mineral with chemical formula K(UO $_2$)(AsO $_4$)·3H $_2$O.
Abernathyite is a transparent, yellow mineral that occurs as tabular crystals up to 3 millimeters (0.12 in), has a single perfect cleavage on {001}, fluoresces yellow-green in longwave and shortwave ultraviolet. Because of its uranium content, the mineral is radioactive.
Abernathyite forms as a coating on fractures of asphaltic sandstone containing uranium deposits, occurs in association with heinrichite, scorodite, and zeunerite. Abernathyite is known from France, Germany, Poland, South Africa, and the United States.

## Acuminites

Acuminite (IMA symbol: Acu) is a rare halide mineral of with chemical formula: SrAlF $_4$(OH)·(H $_2$O). Its name comes from the Latin word acumen, meaning "spear point". Its Mohs scale of mineral hardness rating is 3.5.
Acumenite has only been described from its type locality of the cryolite deposit in Ivigtut, Greenland.

## Adamsites-(Y)

Adamsite-(Y) (previously IMA 1999-020), chemical formula NaY(CO $_3$) $_2$·6H $_2$O is a mineral of sodium, yttrium, carbon, oxygen, and hydrogen, named after Frank Dawson Adams (1859–1942), professor of geology, McGill University, with a Mohs scale rating of 3, IMA symbol is Ads-Y.

## Admontites

Admontite has the chemical formula: MgB $_6$O $_{10}$·7H $_2$O or the repeating unit: MgB $_6$O $_7$(OH) $_6$·4H $_2$O.
Admontite (IMA symbol: Amt) is a hydrated magnesium borate mineral with formula MgB $_6$O $_{10}$·7H $_2$O.
Occurrence - In a gypsum deposit. Associations: gypsum, anhydrite, hexahydrite, löweite, eugsterite, pyrite, quartz.

## Aerinites

Aerinite (Ca $_4$(Al,Fe,Mg) $_{10}$Si $_{12}$O $_{35}$(OH $_{12}$CO $_3$·12H $_2$O) is a bluish-purple inosilicate mineral, that crystallizes in the monoclinic system and occurs as fibrous or compact masses and coatings, has a dark, vitreous luster, a specific gravity of 2.48 and a Mohs hardness of 3. The IMA symbol is Aer.
It is a low-temperature hydrothermal phase occurring in zeolite facies alteration of dolerites. Associated minerals include prehnite,scolecite and mesolite.
Aerinite (Ca $_4$Al,Fe,Mg) $_{10}$Si $_{12}$O $_{35}$(OH) $_{12}$CO $_3$·12H $_2$O) is a bluish-purple inosilicate mineral, that crystallizes in the monoclinic system and occurs as fibrous or compact masses and coatings, has a dark, vitreous luster, a specific gravity of 2.48 and a Mohs hardness of 3. The IMA symbol is Aer.
It is a low-temperature hydrothermal phase occurring in zeolite facies alteration of dolerites. Associated minerals include prehnite, scolecite and mesolite.
Its name comes from a Greek root "aerinos," meaning "atmosphere" or "sky blue". It was first described by Lasaulx (1876) from a specimen in the Wroclaw museum that was obtained in Aragon, Spain. In 1882, the geologist Luis Mariano Vidal found the mineral in situ in Caserras del Castillo, a locality that currently belongs to the municipality of Estopiñán del Castillo, in Huesca (Spain).
Aerinite is a rare mineral. It has been found in several deposits in the Spanish Pyrenees of Huesca and Lleida, as in Estopiñán del Castillo, Camporrells, Juseu and Tartareu. In France, the site is important from St. Pendelon, in the Landes. Aerinite was used as a blue pigment in Romanesque paintings in many churches in the Spain, and also in some French, including the most famous of them, the Pantocrator in the church of San Clemente de Tahull.

## Afwillites

The chemical formula is Ca $_3$(SiO $_3$OH) $_2$·2H $_2$O. Afwillite (IMA symbol: Afw) is a calcium hydroxide nesosilicate mineral that occurs as glassy, colorless to white prismatic monoclinic crystals, has a Mohs scale hardness between 3 and 4, occurs as an alteration mineral in contact metamorphism of limestone, in association with apophyllite, natrolite, thaumasite, merwinite, spurrite, gehlenite, ettringite, portlandite, hillebrandite, foshagite, brucite and calcite.
It was first described in 1925 for an occurrence in the Dutoitspan Mine, Kimberley, South Africa and was named for Alpheus Fuller Williams (1874–1953), a past official of the De Beers diamond company.
Afwillite has had a couple of formulas:
* Ca $_3$Si $_2$O $_4$(OH) $_6$, and
* Ca $_3$(HSiO $_4$) $_2$·2H $_2$O.
Afwillite may form in fractured veins of the mineral spurrite. Jennite, afwillite, oyelite and calcite are all minerals that form in layers within spurrite veins. Afwillite, and calcite, may form from precipitated fluids. Jennite is actually an alteration of afwillite, but both formed from calcium silicates through hydration. Laboratory studies determined that afwillite forms at a temperature below 200 °C (392 °F), usually around 100 °C. Afwillite and spurrite are formed through contact metamorphism of limestone. Contact metamorphism is caused by the interaction of rock with heat and/or fluids from a nearby crystallizing silicate magma.
Structurally, afwillite is a nesosilicate with isolated SiO$_4$ tetrahedra.
Afwillite has two oxides:
* 2SiO$_4$, Silicates, and
* 2H$_2$O, oxidanes, with each having about 50 molecular %.
Calcium does not occur as native calcium. Here it links to the oxygens in the silicate tetrahedra and the oxidanes. Afwillite is 47.6 at % silicate and 28.6 at % oxidane.
Afwillite has a complex monoclinic structure, and the silicon tetrahedra in the crystal structure are held together by hydrogen bonds. It has perfect cleavage]] parallel to its (101) and poor cleavage parallel to its (100) faces. It is biaxial and its 2V angle, the measurement from one optical axis to the other optical axis, is 50 – 56 degrees. When viewed under crossed polarizers in a petrographic microscope, it displays first-order orange colors, giving a maximum birefringence of 0.0167 (determined by using the Michel- Levy chart). Afwillite is optically positive. Additionally, it has a prismatic crystal habit. Under a microscope afwillite looks like wollastonite, which is in the same family as afwillite.
Afwillite is composed of double chains that consist of calcium and silicon polyhedral connected to each other by sharing corners and edges. This causes continuous sheets to form parallel to its miller index [-101] faces. The sheets are bonded together by hydrogen bonds and are all connected by Ca-Si-O bonds (Malik and Jeffery, 1976). Each calcium atom is in 6-fold octahedral coordination with the oxygen, and the silicon is in 4-fold tetrahedral coordination around the oxygen. Around each silicon there is one OH group and there are three oxygens that neighbor them. The silicon tetrahedra are arranged so that they share an edge with calcium(1), and silicon(2) shares edges with the calcium(2) and calcium(3) polyhedral. The silicon tetrahedra are held together by the OH group and hydrogen bonding occurs between the hydrogen in the OH and the silicon tetrahedra. Hydrogen bonding is caused because the positive ion, hydrogen, is attracted to negatively charge ions which, in this case, are the silicon tetrahedra.

## Agardites

Agradite has the chemical formula (REE,Ca)Cu $_6$(AsO $_4$) $_3$(OH) $_6$·3H $_2$O, a repeating unit.
Agardite is a mineral group consisting of agardite-(Y), agardite-(Ce), agardite-(Nd), and agardite-(La). They have been allocated the IMA symbols Agr-Y, Agr-Ce, Agr-Nd and Agr-La. They comprise a group of minerals that are hydrous hydrated arsenates of rare-earth elements (REE) and copper, with the general chemical formula (REE,Ca)Cu $_6$(AsO $_4$) $_3$(OH) $_6$·3H $_2$O. Yttrium, cerium, neodymium, lanthanum, as well as trace to minor amounts of other REEs, are present in their structure. Agardite-(Y) is probably the most often found representative. They form needle-like yellow-green (variably hued) crystals in the hexagonal crystal system. Agardite minerals are a member of the mixite structure group, which has the general chemical formula Cu$^{2+}$ $_6$A(TO $_4$) $_3$(OH) $_6$·3H $_2$O, where A is a REE, Al, Ca, Pb, or Bi, and T is P or As. In addition to the four agardite minerals, the other members of the mixite mineral group are calciopetersite, goudeyite, mixite, petersite-(Ce), petersite-(Y), plumboagardite, and zálesíite.
Agardite-(Y) from the Bou Skour mine in Djebel Sarhro, Morocco was the first of the agardite-group minerals to be characterized. It was described by Dietrich in 1969 and was named after Jules Agard, a French geologist at the Bureau de Recherches Géologiques et Minières, Orléans, France. Agardite-group minerals have subsequently been found in Germany, Czech Republic, Greece, Italy, Japan, Namibia, Poland, Spain, Switzerland, the United Kingdom, and the United States.

## Agrinierites

Agrinierite (K $_2$(Ca,Sr)(UO $_2$) $_3$O $_3$(OH) $_2$·5H $_2$O) is a mineral often found in the oxidation zone of uranium deposits. The 'IMA symbol is Agn. It is named for Henry Agrinier (1928–1971), an engineer for the Commissariat à l'Énergie Atomique.
Chemical formula for Agrinierite is (K $_2$,Ca,Sr)U $_3$O $_{10}$·4(H $_2$O).
Formula for Agrinierite is K $_2$(Ca,Sr)[(UO $_2$) $_3$O $_3$(OH) $_2$] $_2$·5H $_2$O.

## Ahlfeldites

Ahlfeldite ((Ni,Co)SeO $_3$·2H $_2$O) is a mineral of secondary origin with the International Mineralogical Association (IMA) symbol Afe, named after Friedrich Ahlfeld (1892–1982), a German-Bolivian mining engineer and geologist, a type locality of Virgen de Surumi mine, Pakajake Canyon, Chayanta Province, Potosí Department, Bolivia.
In the image on the right is a druse of tiny alfredopetrovite crystals, colorless to greyish tone, coating over blue chalcomenite and pink ahlfeldite, on a kruťait-penroseite matrix. Some areas, with no colored background minerals, let us to see perfectly crystals. You can also observe face reflections of this extremely rare species. Alfredopetrovite is the first aluminium selenite mineral.

## Ajoites

Ajoite has the chemical formula (Na,K)Cu $_7$AlSi $_9$O $_{24}$(OH) $_6$·3H $_2$O, and minor Mn, Fe and Ca are usually also present in the structure. Ajoite is used as a minor ore of copper.
Ajoite (International Mineralogical Association (IMA) symbol Aj) is a hydrated sodium potassium copper aluminium silicate hydroxide mineral.
Ajoite is a secondary mineral that forms from the oxidation of other secondary copper minerals in copper-rich base metal deposits in massive fracture coatings, in vein fillings, and in vugs. It may form from shattuckite and also it may be replaced by shattuckite.
At the type locality it is associated with shattuckite, conichalcite, quartz, muscovite and pyrite.
Ajoite is named after its type locality, the New Cornelia Mine in the Ajo District of Pima County, Arizona. Type specimen material is conserved at the National Museum of Natural History, Washington DC, USA, reference number 113220.
Other localities include Wickenburg and Maricopa County, Arizona, within the United States, and the Messina (Musina) District in South Africa. Quartz specimens from the defunct Messina Mines on the border between Zimbabwe and South Africa are well known for their inclusions of blue copper silicate minerals such as shattuckite, papagoite and ajoite, but ajoite from American localities does not occur like this.

## Aksaites

Aksaites have the formula Mg[B $_6$O $_7$(OH) $_6$] · 2H $_2$O, IMA symbol is Aks, IMA formula: MgB $_6$O $_7$(OH) $_6$ · 2H $_2$O.
Aksaite is orthorhombic.
"According to the results of the structural analysis, the largest thermal motion is shown by the water molecule, O(14), which is only linked to the Mg atom and to O(13") through a hydrogen bond. The thermal amplitude of two of the three triangular hydroxyls, O(11) and O(13), involved in a bond with boron as well as in two hydrogen bonds, is rather large. Much smaller is the displacement of the O(12) hydroxyl which is also participating to a bond with magnesium. It is also easy to understand the slight thermal motion of the water molecule O(15), which is involved in a bond with magnesium and in three hydrogen bonds as well."

## Albrechtschraufites

Albrechtschraufite (International Mineralogical Association (IMA) symbol: Asf) is a very rare complex hydrated calcium and magnesium-bearing uranyl fluoride carbonate mineral with formula Ca $_4$Mg(UO $_2$) $_2$(CO $_3$) $_6$F $_2$·17H $_2$O. Its molar weight is 1,428.98 g, color yellow-green, streak white, density 2.6 g/cm$^3$, Mohs hardness 2-3, and luster is vitreous (glassy). It is named after Albrecht Schrauf (1837–1897), Professor of Mineralogy, University of Vienna. Its type locality is Jáchymov, Jáchymov District, Krušné Hory Mountains, Karlovy Vary Region, Bohemia, Czech Republic.

## Aldermanites

Aldermanite (International Mineralogical Association (IMA) symbol: Adm) is a rare hydrated phosphate mineral with formula Mg $_5$Al $_{12}$(PO $_4$) $_8$(OH) $_{22}$·32H $_2$O. It's named after Arthur Richard Alderman (1901–1980), Professor of Geology and Mineralogy, University of Adelaide. Its type locality is Moculta Phosphate Quarry (Klemm's Quarry), Angaston, Barossa Valley, North Mount Lofty Ranges, Mount Lofty Ranges, South Australia, Australia.

## Aliettites

Aliettite (International Mineralogical Association (IMA) symbol: Ali) is a complex phyllosilicate mineral of the smectite group with a formula of (Ca $_{0.2}$Mg $_6$(Si,Al) $_8$O $_{20}$(OH) $_4$·4H $_2$O) or [Mg $_3$Si $_4$O $_{10}$(OH) $_2$](Ca $_{0.5}$,Na) $_{0.33}$(Al,Mg,Fe$^{2+}$ ) $_{2–3}$(Si,Al) $_4$O $_{10}$(OH) $_2$·n(H $_2$O).
It is a soft, colorless to pale yellow or green earthy mineral which crystallizes in the monoclinic system as minute tabular to platy crystals.
It was first described in 1968 for an occurrence in Monte Chiaro, Albareto, Parma Province, Emilia-Romagna, Italy and named for the Italian mineralogist Andrea Alietti (born 1923).
A regularly interstratified talc-saponite mineral.
Common Impurities: Mn.
Common Associates: Calcite CaCO $_3$, Chlorite Group A group of mostly monoclinic (also triclinic or orthorhombic) micaceous phyllosilicate minerals with a structure consisting of T-O-T layers with two layers having their silicate tetrahedral apices pointing towards each other, separated by an interlayer that may be simple octahedrally coordinated cations or which may be a brucite-*like* layer of two sheets of closely packed OH groups with the interstices between sheets providing the octahedral coordination site; the T-O-T layers and interlayer are bonded by electrostatic and hydrogen bonding forces; as the "a" and "b" directions of the T-O-T layer may be oriented to the interlayer "a" and "b" directions in twelve different stacking sequences, resulting in twelve different polytype possibilities (not all of which have been found in Nature yet for each species), Serpentine Subgroup D $_3$[Si $_2$O $_5$](OH) $_4$, D = Mg, Fe, Ni, Mn, Al, Zn, Talc Mg $_3$Si $_4$O $_{10}$(OH) $_2$.
It occurs in serpentinized ophiolites and their residual soil. It also occurs in altered dolomite. Associated minerals include talc, chlorite, serpentine and calcite. In addition to the type locality in Italy it has been reported from Kinshasa, Katanga; the Chelyabinsk Oblast of the southern Urals and the Turii alkaline Massif of the Kola Peninsula in Russia; the Zirabulak Mountains of Uzbekistan; and the Goldstrike Mine of Eureka County, Nevada, US.

## Allanpringites

Allanpringite has the formula: Fe$^{3+}$ $_3$(PO $_4$) $_2$(OH) $_3$·5H $_2$O.
Allanpringite (International Mineralogical Association (IMA) symbol: Apg) is a phosphate mineral named after Australian mineralogist Allan Pring of the South Australian Museum, an Fe$^{3+}$ analogue Al-phosphate mineral wavellite, but it has a different crystal symmetry – monoclinic instead of orthorhombic in wavellite, forms needle-like crystals, which are always twinned and form parallel bundles up to about 2 mm long, are often found in association with other iron phosphates in abandoned iron mines.

## Alluaivites

Alluaivite (International Mineralogical Association (IMA) symbol: Aav) is a rare mineral of the eudialyte group, with complex formula written as Na $_{19}$(Ca,Mn$^{2+}$ ) $_6$(Ti,Nb) $_3$Si $_{26}$O $_{74}$Cl·2H $_2$O. The two dual-nature minerals of the group, being both titano- and zirconosilicates, labyrinthite and dualite, respectively, contain the alluaivite module in their structures. Alluaivite is named after Mt. Alluaiv in Lovozero Tundry massif, Kola Peninsula, Russia, where it is found in ultra-agpaitic, hyperalkaline pegmatites.
Alluaivite contains relatively high amounts of admixing strontium, cerium, potassium, and barium, with lesser amounts of substituting lanthanum and zirconium.
Alluaivite was found in ultra-agpaitic (highly alkaline) pegmatites on Mt. Alluaiv, Lovozero massif, Kola Peninsula, Russia - hence its name. Associating minerals are aegirine, arfvedsonite, eudialyte, nepheline, potassic feldspar, and sodalite.

## Althupites

Althupite (International Mineralogical Association (IMA) symbol: Ahp) is a rare aluminium thorium uranyl phosphate mineral, named after its composition (ALuminium, THorium, Uranium, and Phosphorus), with a complex formula written as AlTh(UO $_2$) $_7$(PO $_4$) $_4$O $_2$(OH) $_5$·15H $_2$O, from a granitic pegmatite.

## Alum-(K)s

Alum-(K) is a hydrous potassium aluminium sulfate mineral with formula KAl(SO $_4$) $_2$·12(H $_2$O). It's International Mineralogical Association (IMA) symbol is Aum-K. It is the mineral form of potassium alum and is referred to as potassium alum in older sources. It is a member of the alum group.
It occurs as colorless to white, soft isometric crystals and efflorescence coatings. Rare crystals are octahedral in form if occurring as precipitates from neutral water solution, but cubic in form if the solution is alkaline.
It occurs as a precipitate around volcanic fumaroles and solfataras. It also occurs as an alteration in argillaceous sediments or coal beds which contain oxidizing sulfide minerals (pyrite or marcasite). Occurs associated with alunogen, pickeringite, epsomite, melanterite, gypsum and native sulfur.
Occurrences include Mount Vesuvius, Italy and Alum Cave, Sevier County, Tennessee.

## Aluminites

Chemical formula: Al $_2$(SO $_4$)(OH) $_4$•7H $_2$O.
Crystal system: Monoclinic.
Member of the Aluminite Group.
Other Members of this group: Mangazeite Al $_2$(SO $_4$)(OH) $_4$·3H $_2$O.
Occurrence: "Typically in clays or lignites, formed by the reaction of sulfate-bearing solutions from the decomposition of marcasite or pyrite at moderate temperatures with aluminous silicates; as a volcanic sublimate; in sulfur deposits; rarely in caves."
"Found as earthy reniform or nodular masses composed of tiny fibrous crystals."
Geological Setting: "Found as concretionary deposits in Tertiary to Quaternary clays, marls, and lignites, formed by the action of sulfate solutions derived from the decay of pyrite or marcasite on aluminous silicates. Typically in clays or lignites, formed by the reaction of sulfate-bearing solutions from the decomposition of marcasite or pyrite at moderate temperatures with aluminous silicates; as a volcanic sublimate; in sulfur deposits; rarely in caves."
Association: "Basaluminite, gibbsite, epsomite, gypsum, celestine, dolomite, goethite."

## Alunogens

Alunogen is a colourless to white (although often coloured by impurities, such as iron substituting for aluminium) fibrous to needle-like aluminium sulfate mineral with the International Mineralogical Association (IMA) symbol of Alg, and the chemical formula Al $_2$(SO $_4$) $_3$·17H $_2$O.
Occurrence: Forms by reaction of sulfates from decomposing sulfides with aluminous minerals in shales and slates; in gossan or altered wall rock of pyritic deposits in arid regions; in coal seams; in relatively low-temperature fumaroles.
Environment: Secondary mineral commonly associated with coals and pyritiferous shales in arid regions.
Alunogen is often found on the walls of mines and quarries as a secondary mineral, in the oxidation zones of some ore deposits as well as on burning coal dumps (i.e., as the product of millosevichite hydration), forms as a low temperature deposit in fumaroles, and occurs associated with pyrite, marcasite, halotrichite, pickeringite, epsomite, potash alum, melanterite and gypsum.
"At high temperates, alunogen may dehydrate to its pentahydrate, Unnamed (Al Sulphate-Hydrate)."
The crystallochemical formula, can be written as: [Al(H $_2$O) $_6$] $_2$(SO $_4$) $_3$.5H $_2$O. The second formula shows that H $_2$O in the alunogen formula occurs both as a ligand (coordinative form) and a loosely bound (crystallization) form.

## Annabergites

Annabergite is an arsenate mineral consisting of a hydrous nickel arsenate, Ni $_3$(AsO $_4$) $_2$·8H $_2$O, crystallizing in the monoclinic system and isomorphous with vivianite and erythrite. Crystals are minute and capillary and rarely met with, the mineral occurring usually as soft earthy masses and encrustations. A fine apple-green color is its characteristic feature. It was long known (since 1758) under the name nickel bloom; the name annabergite was proposed by H. J. Brooke and W H. Miller in 1852, from Annaberg in Saxony, one of the localities of the mineral. It occurs with ores of nickel, of which it is a product of alteration. A variety, from Creetown in Kirkcudbrightshire, in which a portion of the nickel is replaced by calcium, has been called dudgeonite, after P. Dudgeon, who found it.
Closely related is cabrerite wherein some of the nickel is replaced by magnesium. It is named for Sierra Cabrera in Spain where it was originally found.

## Autunites

[[Image:Autunite-rl-aut8a.jpg|thumb|left|thumb|224x224px|Autunite is from Mount Kit Carson, Washington. Credit: Robert M. Lavinsky.{{tlx|free media]]
Autinite has the chemical formula Ca(UO $_2$) $_2$(PO $_4$) $_2$·10–12H $_2$O.
Autunite (hydrated calcium uranyl phosphate) is a yellow-greenish fluorescent phosphate mineral with a Mohs hardness of 2–​2 $^1$⁄$_2$. Autunite crystallizes in the orthorhombic system and often occurs as tabular square crystals, commonly in small crusts or in fan-like masses. Due to the moderate uranium content of 48.27% it is radioactive and also used as uranium ore. Autunite fluoresces bright green to lime green under UV light. The mineral is also called calco-uranite, but this name is rarely used and effectively outdated.
Autunite was discovered in 1852 near Autun, France, which is also autunite's namesake, occurs as an oxidation product of uranium minerals in granite pegmatites and hydrothermal deposits, with associate minerals: metaautunite, torbernite, phosphuranylite, saleeite, uranophane and sabugalite.
Autunite was found inside the Daybreak Mine on Mount Kit Carson, Spokane, Washington (or sometimes referred to as "near Mount Spokane"), in "vugs, fractures, and shear zones in granitic rock", that showed signs of another phosphate, apatite, which may have helped lead to the formation of autunite, by providing a source of phosphate and lime, where the formation may have occurred with the interaction of uranium leached from a separate deposit.
Elements usually emit a gamma-ray during nuclear decay or fission. The gamma-ray spectrum at right shows typical peaks for $^{226}$ Ra, $^{214}$ Pb, and $^{214}$ Bi. These isotopes are part of the uranium-radium decay line. As $^{238}$ U is an alpha-ray emitter, it is not shown. The peak at 40 keV is not from the mineral. From the color of the rock shown the yellowish mineral is likely to be autunite.

## Calumetites

Calumetite has the chemical formula Cu(OH,Cl)$_2$·2H$_2$O.
Calumetite has been found in association with tremolite, quartz, epidote, monazite, copper, cuprite, atacamite, buttgenbachite, malachite, paratacamite, and anthonyite.
The specific gravity of calumetite could not be measured because of the difficulty in separating the quartz and epidote from the calumetite mineral coating them.
Other copper minerals have been linked to calumetite which include copper, cuprite, malachite, atacamite, paratacamite, buttgenbachite.
Calumetite has been stated to be a naturally occurring mineral.
Calumetite is insoluble in ammonia and water, and soluble in cold dilute acids.
Calumetite has been noted to be useful in paintings on canvas and fresco.

## Carnotites

Carnotite is a potassium uranium vanadate radioactive mineral with chemical formula: K $_2$(UO $_2$) $_2$(VO $_4$) $_2$·3H $_2$O. The water content can vary and small amounts of calcium, barium, magnesium, iron, and sodium are often present. Carnotite is a bright yellow to greenish yellow mineral that occurs typically as crusts and flakes in sandstones. Amounts as low as one percent will color the sandstone a bright yellow. The high uranium content makes carnotite an important uranium ore and also radioactive. It is a secondary vanadium and uranium mineral usually found in sedimentary rocks in arid climates. It is an important ore of uranium in the Colorado Plateau region of the United States where it occurs as disseminations in sandstone and concentrations around petrified logs.

## Carrboydites

Carrboydite has the formula: (Ni $_{(1-x)}$Al $_x$)(SO $_4$) $_{(x/2)}$(OH) $_2$·nH $_2$O, where (x < 0.5, n > 3x/2), is a member of the Glaucocerinite Group > Hydrotalcite Supergroup, in the Hexagonal Crystal System, named for the Carr Boyd nickel mine, Australia, the type locality.
Carrboydite has the Chemical Formula: (Ni,Cu) $_{14}$Al $_9$(SO $_4$,CO $_3$)(OH) $_{43}$•7(H $_2$O). The Empirical Formula is Ni $_{10}$Cu $_4$Al $_9$(SO $_4$) $_4$(CO $_3$) $_2$(OH) $_{43}$•7(H $_2$O).
"As part of the recent re-evaluation of the nomenclature of the hydrotalcite supergroup (Mills et al., 2012), carrboydite was identified as a questionable species which needs further investigation."
Environment: "Surface material at a nickel mine."

## Dwornikites

The monohydrate occurs as very rare mineral dwornikite (Ni,Fe)SO $_4$·H $_2$O.
The mineral occurs as sharp yellow-greenish acicular crystals covering a great part of the matrix.

## Epsomites

Crystal structure of epsomite - MgSO$_4$·7H$_2$O.
Orthorhombic "MgSO $_4$·7H $_2$O epsomite, with which morenosite is isostructural, dehydrates to the monoclinic polymorph of MgSO $_4$·6H $_2$O (hexahydrite) and not to the tetragonal phaseas in the caseof morenosite."
Epsomite forms as encrustations or efflorescences on limestone cavern walls and mine timbers and walls, rarely as volcanic fumarole deposits, and as rare beds in evaporite layers such as those found in certain bodies of salt water. It was first systematically described in 1806 for an occurrence near Epsom, Surrey, England, after which it was named, occurs in association with melanterite, gypsum, halotrichite, pickeringite, alunogen, rozenite and mirabilite.
Epsomite dehydrates in air.
The epsomite group includes solid solution series with morenosite (NiSO$_4$·7H$_2$O) and goslarite (ZnSO$_4$·7H$_2$O)

## Garnierites

Chemical analysis of garnierite samples yields non-stoichiometric formulae that can be reduced to formulas like those of talc and serpentine suggesting a talc monohydrate formula of H $_2$O(Mg,Ni) $_3$Si $_4$O $_{10}$(OH) $_2$ for the talc-like garnierite.
The main difference between the serpentine-like and talc-like variants of garnierite is the spacing between layers in the structure, seen in x-ray powder diffraction studies. The serpentine-like variants have 7 Å basal spacings while the talc-like variants have a basal spacing of 10 Å.
Garnierite is a layer silicate.
7 Å type garnierites usually resemble chrysotile or lizardite in their structures, while 10 Å types usually resemble pimelite.
The color comes from the presence of nickel in the mineral structure for magnesium.

## Hydrohonessites

In the image on the right, hydrohonessite was riginally described as jamborite, now most green coatings on millerite like this have been shown to be hydrohonessite per David Hospital.
Hydrohonessite has the formula: (Ni $_{1-x}$Fe$^{3+}$ $_x$)(OH) $_2$(SO $_4$) $_{x/2}$ · nH $_2$O (x > 0.5, n > ​$^{3x}$⁄$_2$.
"May convert readily into honessite, depending on humidity and temperature. Appears to be stable between pH 6 and 7."
General Appearance of Type Material: Thin surface encrustation of tiny hexagonal crystals on botryoidal quartz and magnesite in a fracture in supergene Ni-Fe sulphides.
Associated Minerals at Type Locality: Quartz, Magnesite, Violarite, Pyrite, Gaspéite, Goethite, Pecoraite and Gypsum.
"A precipitate corresponding to hydrohonessite was obtained by slowly adding an aqueous 0.1 M ferrous sulphate solution to a 0.1 M nickel sulphate solution. The pH of the solution was maintained between 6.0 and 6.5 by the addition of 0.01 M sodium carbonate. Above pH 7.5, Ni(OH) $_2$ is precipitated, and below pH 6, FeOOH. The oxidation of the iron and precipitation of the hydrohonessite is slow, so care must be taken that the pH does not drop too low during the approximately 24 hours that the precipitation requires. After drying at 25°C, the precipitate gives a diffuse X-ray powder pattern similar to that of hydrohonessite. Chemical analysis of the precipitate confirmed that the composition is close to that of hydrohonessite. The infra-red spectrum of the synthetic hydrohonessite [...] is similar to that of honessite (Bish and Livingstone, 1981), and is characterized by strong absorptions due to H $_2$O and SO $_4$. The synthetic hydrohonessite dehydrates slowly at 25°C, and after ten days it gives a diffuse X-ray diffraction pattern of four lines which correspond to the strongest lines of the honessite diffraction pattern (Bish and Livingstone, 1981), i.e. with a basal spacing in the neighbourhood of 9 Å; the conversion can also be achieved more rapidly by heating the synthetic hydrohonessite at 110°C. The natural hydrohonessite is more stable than its synthetic equivalent, since it retains its integrity at 110°C, and dehydration requires a temperature between 150 and 170°C. The dehydration experiments indicate that hydrohonessite is the hydrated equivalent of honessite."

## Kambaldaites

Kambaldaites have the formula: NaNi $_4$(CO $_3$) $_3$(OH) $_3$ · 3H $_2$O.
General Appearance of Type Material: Cryptocrystalline veins, layers and concretionary growths up to about 2 mm thick, commonly intergrown with gaspeite, also as encrustations of tiny hexagonal prisms.
Geological Setting of Type Material: Nickel sulfide deposit, as a secondary mineral that has been precipitated on fracture surfaces in oxidizing Ni-Fe sulfide ore.
"The primary sulfides, which occur as assemblages of pentlandite-pyrrhotite-pyrite and pentlandite-millerite-pyrite, have been altered to supergene assemblages consisting largely of violarite and pyrite, which have decomposed on further oxidation to a goethitic residue in which the secondary nickel minerals have been deposited."
"The samples in which the kambaldaite was found are from a depth of about 20 meters, and consist largely of goethite with some reevesite and residual pyrite. The kambaldaite, together with gaspeite and some aragonite, occurs on fracture surfaces in the goethite. The kambaldaite occurs in a variety of types: massive, crystalline, nodular and chalky."

## Lavendulans

Lavendulan has the chemical formula (Ca,Na)$_2$Cu$_5$(AsO$_4$)$_4$Cl·4-5H$_2$O.

## Minasragrites

Retgersite "occurs with morenosite, described beyond in more detail, and with blue efflorescent masses of minasragrite, V $_2$H $_2$(SO $_4$) $_3$O $_2$·15H $_2$O. The latter substance unquestionably has formed at least in part since the specimen was collected but both the retgersite and morenosite appear to be original deposits. Both minerals presumably were formed ultimately by the oxidation of nickelian pyrite present in the ore-body."

## Morenosites

The heptahydrate nickel sulfate NiSO $_4$.7H $_2$O, which is relatively unstable in air, occurs as morenosite.
"On standing in the open in dry air, crystals of morenosite generally dehydrate rapidly to the tetragonal hexahydrate, retgersite. This was verified by the writers on several artificial preparations. The product formed, however, varies considerably with circumstances. One artificial preparation, crystallized from a water solution containing a little HCl, proved to be stable under ordinary conditions. Further, the natural morenosite from Minasragra had partially effloresced during the thirty years or so that it had been contained in the collection, but the dehydration product proved to be not the hexahydrate but a mixture of several lower hydrates."
A "complete series extends between the orthorhombic compounds morenosite, NiSO $_4$·7H $_2$O, and epsomite, MgSO $_4$·7H $_2$O, as shown by Dufet (5) and by Hutton (10)."
"Retgersite can be synthesized by crystallization from pure water solution at temperatures between 31.5°, below which orthorhombic NiSO $_4$·7H $_2$O is stable, and 53.3°, above which monoclinic NiSO $_4$·6H $_2$O is stable. A dihydrate forms above about 118°. These transition temperatures are from the data of Steele and Johnson (17); slightly different values have been reported by others (see Seidell (17)), and metastable equilibria commonly occur. Retgersite also can crystallize at temperatures at least as low as 0° from solutions which contain an appropriate excess of free H $_2$SO $_4$, as shown by Rohmer (14) and others. This factor may determine its formation in nature in place of morenosite. Under certain circumstances both retgersite and morenosite have been observed to crystallize simultaneously, one or the other of the two compounds being in metastable equilibrium."

## Otwayites

Otwayite has the chemical formula Ni $_2$CO $_3$(OH) $_2$.
Otwayite has the formula: Ni $_2$CO $_3$(OH) $_2$ · H $_2$O.
Geological Setting of Type Material: Narrow veinlets to 1 mm in width, probably late-stage fracture filling, transecting nickeloan serpentine, millerite, polydymite, and apatite.
Otwayite is associated with Widgiemoolthalite.
Occurrence: Otwayite is found in association with nullaginite and hellyerite in the Otway nickel deposit, is found in association with theoprastite, hellyerite, gaspeite and a suite of other nickel carbonate minerals in the Lord Brassey Mine, Tasmania, in association with gaspeite, hellyerite and kambaldaite in the Widgie Townsite nickel gossan, Widgiemooltha, Western Australia, and reported from the Pafuri nickel deposit, South Africa.
It was first described in 1977 from the Otway Nickel Deposit, Nullagine, Pilbara Craton, Western Australia and named for Australian prospector Charles Albert Otway (born 1922).

## Reevesites

Chemical Formula: Ni $_6$Fe$^{3+}$ $_2$(CO $_3$)(OH) $_{16}$•4(H $_2$O).
Environment: Alteration product of a highly weathered iron-nickel meteorite.
Type Locality: Wolf Creek meteorite, found three km west of the Scotia talc mine, Bon Accord area, Barberton, Transvaal, South Africa.
Crystal System: Trigonal.
Member of the Hydrotalcite Group > Hydrotalcite Supergroup.
Geological Setting: Nickel rich ore deposits.
Geological Setting of Type Material: alteration product of a highly weathered iron-nickel meteorite.
Associated Minerals at Type Locality: Goethite, Jarosite, Serpentine Subgroup, Apatite, Lipscombite.

## Retgersites

Aqueous solutions of nickel sulfate react with sodium carbonate to precipitate nickel carbonate, a precursor to nickel-based catalysts and pigments. Addition of ammonium sulfate to concentrated aqueous solutions of nickel sulfate precipitates Ni(NH$_4$)$_2$(SO$_4$)$_2$·6H$_2$O, a blue-coloured solid analogous to Mohr's salt, Fe(NH$_4$)$_2$(SO$_4$)$_2$·6H$_2$O.
Nickel sulfate occurs as the rare mineral retgersite, which is a hexahydrate. Retgersite has the chemical formula NiSO $_4$•6H $_2$O.
"Oxidization zone of nickel-bearing hydrothermal mineral deposits, formed from H $_2$O solution between 31.5 deg C and 53.5 deg C. Dimorphous with nickelhexahydrite."
"May occur as a dehydration product of morenosite."
"The tetragonal polymorph of NiSO $_4$•6H $_2$O was first identified [...] as poorly formed, bluish green crystals incrusting a black coke-like mass of patronite from Minasragra, Peru."
Natural "occurrences of retgersite [...] comprised a foot-long mass of niccolite-bearing vein material from a mine in Cottonwood Canyon, Churchill County, Nevada [...]. The geology of the deposit has been described by Ferguson (6). The specimen has been thoroughly oxidized and is crusted over and veined by apple-green, granular masses of annabergite and blue-green fibrous aggregates of retgersite. The retgersiteis an original deposit, in part earlier formed than annabergite, and is not a dehydration product of morenosite."
"The Mg and part at least of the Fe$^{2+}$ is present in substitution for Ni."
"Retgersite is isostructural with the tetragonal polymorphs of the hexahydrated selenates of Ni and Zn."
"The monoclinic polymorph of NiSO $_4$•6H $_2$O has been prepared artificially and its crystallographic and optical properties have been described (8,9). This compound, green in color, is formed from pure water solutions at temperatures over 53.3°C. and below this temperature rapidly inverts to the blue tetragonal polymorph. The occurrence of this unstable and relatively soluble (52.5g. NiSO $_4$ in 100g. water at 54.5°) monoclinic phase in nature seems very unlikely. The monoclinic zinc and magnesium analogues are stable under ordinary conditions, however, and occur in nature as the minerals bianchite and hexahydrite."

## Takovites

Takovites have the formula: Ni $_6$Al $_2$(OH) $_{16}$(CO $_3$) · 4H $_2$O.
Member of the Hydrotalcite Group > Hydrotalcite Supergroup.
Morphology: Microcrystalline, platy, to 1 µm; commonly in veinlets and massive.

## Torbernites

Torbernite is a radioactive, hydrated green copper uranyl phosphate mineral, found in granites and other uranium-bearing deposits as a secondary mineral. Torbernite is isostructural with the related uranium mineral, autunite. The chemical formula of torbenite is similar to that of autunite in which a Cu$^{2+}$ cation replaces a Ca$^{2+}$. The number of water hydration molecules can vary between 12 and 8, giving rise to the variety of metatorbernite when torbernite spontaneously dehydrates. Torbernite has the chemical formula Cu(UO $_2$) $_2$(PO $_4$) $_2$ • 12H $_2$O.

## Tungstites

Tungstite is a hydrous tungsten oxide mineral with formula: WO $_3$·H $_2$O, a secondary mineral formed by the weathering [alteration] of other tungsten containing minerals, crystallizes in the orthorhombic system in translucent yellow to yellow green masses, is clay-like with Mohs hardness of 2.5 and a specific gravity of 5.5.
Occurs as an "alteration product of tungsten minerals, especially wolframite and ferberite, in hydrothermal tungsten-bearing deposits."

## Uranophanes

Uranophane Ca(UO $_2$) $_2$(SiO $_3$OH) $_2$·5H $_2$O is a rare calcium uranium [nesosilicate] hydrate mineral that forms from the oxidation of uranium bearing minerals. Uranophane is also known as uranotile. It has a yellow color and is radioactive.

## Widgiemoolthalites

"Widgiemoolthalite is a rare hydrated nickel(II) carbonate mineral with the chemical formula (Ni,Mg)$_5$(CO$_3$)$_4$(OH)$_2$·5H$_2$O. Usually bluish-green in color, it is a brittle mineral formed during the weathering of nickel sulfide. Present on gaspéite surfaces".

## Hypotheses

* Variations in rocks from one mineral composition into another can occur with each rock type.
* Oxidanes that are various ices may be produced by orbital cycling.