Diamond

== Description ==
A stable, extremely hard, crystalline form of carbon that occurs naturally. Diamonds were known to man prior to 800 BCE from alluvial deposits found in India, Sumatra, and Borneo. They were discovered in Brazil in 1725, in South Africa in 1867, and in Arkansas in 1906. The finest grade diamonds are transparent, brilliant stones that are used as gems; these are primarily mined from the kimberlite pipes in South Africa, and glacial tills of Zaire and Brazil. The largest diamond in the world, the Cullinan diamond, was found in 1905 in South Africa. Named for Sir Thomas Cullinan, it has since been cut into 9 large stones, the largest of which, Great Star of Africa (530.2 carat), is set in the British royal scepter. Diamonds with some imperfections are classified as industrial grade and are used for cutting tools and delicate instruments. These are primarily mined in Australia, Brazil, and South Africa. Abrasive pastes are made from small, imperfectly crystallized pieces called bort (rounded with no distinct cleavage), ballas, and carbonado (black diamond, usually granular with no distinct cleavage). Synthetic diamonds, produced using high heat and pressure, are also used as abrasives. Imitation diamonds have been made from lead glass (paste diamond), quartz rock crystal (rhinestone), cubic zirconia, synthetic rutile, and synthetic spinel.
Properties of Natural and Simulated Diamonds
Gem 	Source 	Composition 	Common dates of use	Mohs' hardness	Refractive index 	Specific gravity	Dispersion 	Crystal indices 	Fluorescence 	Optical 	Other
Corundum 	natural or synthetic	Al2O3 	1900- 1947 	9 	epsilon = 1.757-1.768; omega = 1.765-1.776	3.96- 4.05 	0.018 	hexagonal crystal system with tabular, prismatic or pyramidal crystals; fracture = conchoidal	orange to red; heat treated stones may fluoresce green 	marked dichroism 	natural inclusions minerals and fluid are common; synthetic may have gas bubbles and curved striae; low thermal conductivity
Cubic zirconia 	synthetic 	ZrSiO4 	1976 - present 	8.5 	2.15-2.18 	5.6-6.0 	0.06 	fracture = conchoidal 	yellow fluorescence in shortwave UV 	 	usually no inclusions; low thermal conductivity
Diamond 	natural 	C 	1476 - present 	10 	2.4175 	3.51- 3.53 	0.044 	cubic crystal system; perfect cleavage in four directions. 	may fluoresce pale colors in longwave UV; may phosphoresce 	 	Numerous inclusions; trigonal on surface; very high thermal conductivity
Garnet 	synthetic 	YAG/GGG 	1970- 1976 	8.25/7.0 	1.87/1.97 	4.6/7.0 	0.028/ 0.045	cubic crystal system 	 	isotropic 	turns brown in UV light; low thermal conductivity
Moissanite 	synthetic 	silicon carbide 	1998 - present 	8.5-8.25 	2.65-2.69 	3.22 	0.104 	 	may have pale fluorescence 	strongly birefringent; anisotropic	may have brown tint; resistant to heat; inclusions occur as fine white tubes; high thermal conductivity
Paste diamond 	synthetic 	high lead glass 	1700 - present 	5.0-6.0 	1.67 	2.4-4.2 	>0.02 	 	 	highly refractive 	low thermal conductivity; used since 1700
Quartz 	natural 	SiO2 	 	7 	epsilon = 1.553; omega = 1.544 	2.65- 2.66 	 	trigonal crystal system; low birefringence; fracture = conchoidal 	 	low birefringence 	heat treatments may bleach stones; low thermal conductivity; low thermal expansion;
Rutile 	synthetic 	TiO2 	1947- 1955 	6 	2.6-2.9 	4.25 	0.33 	 	 	doubly refractive 	may have yellow tint; low thermal conductivity
Spinel 	natural or synthetic	MgAl2O4 	1920- 1947 	8 	1.715-1.725 	3.5-4.1 	0.02 	isometric crystal system; fracture = conchoidal 	natural fluoresces red in longwave; synthetic may fluoresce in shortwave	anisotropic 	Natural stone has octahedral inclusions; may have fingerprint patterns; low thermal conductivity
Strontium titantate	synthetic 	SrTiO3 	1955- 1970 	5.5 	2.41 	5.13 	0.19 	 	 	 	low thermal conductivity
Tourmaline 	natural 	aluminum borosilicate	 	7-7.5 	epsilon = 1.610-1.650; omega = 1.635-1.675	2.9-3.2 	 	hexagonal, prismatic crystals; fracture = conchoidal 	little fluorescence 	pleochroic; high birefringence 	inclusions include gas or liquid pockets and color zoning; develops electrical charge when heated
Zircon 	natural 	ZrSiO4 	 	6.0 - 7.5 	epsilon = 1.968-2.015; omega = 1.923-1.960	4.6-4.7 	0.039 	tetragonal system with square prismatic crystals; brittle; fracture = uneven 	some show dull yellow color; some may phosphoresce 	pleochroic; high birefringence 	heating brown zircon crystals produces strong colors (blue, green, red, etc.) that fade slowly with time or with UV exposure; low thermal conductivity
== Synonyms and Related Terms ==
bort; carbonado; ballas; Cullinan diamond; Great Star of Africa; adamas (ancient Greek); diamant (Ces., Dan., Fr., Ned., Sven.); Diamant (Deut.); diamante (Esp., It., Port.); diament (Pol.)
== Risks ==
[[[SliderGallery rightalign|diamondRS.jpg~Raman (RASMIN)|Diamond Raman RRUFF R150089.png~Raman (RRUFF)]]]
* No significant hazards.
==Physical and Chemical Properties==
* Hardest natural material. 
* Cubic crystal system. 
* Perfect cleavage in four directions. 
* Luster = greasy to adamantine. 
* Streak = colorless. 
* Fluorescence: natural diamonds may fluoresce blue (type I) or orange (type II). Irradiated diamonds have a strong orange fluorescence in both LW and SW, Synthetic diamonds range from inert to strong orange fluorescence; some may phosphoresce.
* Birefringence = none
Mohs Hardness 	10
Melting Point 	3700 C
Boiling Point 	4200 C
Density 	3.51-3.53 g/ml
Refractive Index	2.417-2.4195
Dispersion 	0.044 (moderate fire)
== For easy print and to download ==
==Resources and Citations==
* Gem Identification Lab Manual, Gemological Institute of America, 2016. (fluorescence information)
* Mineralogy Database: Diamond
* Jack Odgen, Jewellery of the Ancient World, Rizzoli International Publications Inc., New York City, 1982
* R.F.Symmes, T.T.Harding, Paul Taylor, Rocks, Fossils and Gems, DK Publishing, Inc., New York City, 1997
* Encyclopedia Britannica, http://www.britannica.com Comment: "diamond" [Accessed March 4, 2002].
* Website: http://www.geo.utexas.edu/courses/347k/redesign/gem_notes/Diamond/diamond_triple_frame.htm (fluorescence information)
* Wikipedia: http://en.wikipedia.org/wiki/Diamond (Accessed Mar. 1, 2006) (synonyms)
* Yasukazu Suwa, Gemstones: Quality and Value, Volume 1, Sekai Bunka Publishing Inc., Tokyo, 1999 Comment: RI=2.417; Specific gravity=3.52;
* Michael O'Donoghue and Louise Joyner, Identification of Gemstones, Butterworth-Heinemann, Oxford, 2003 Comment: RI=2.417; Specific gravity=3.52; dispersion=0.44
* Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
* The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
* G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971
* Michael McCann, Artist Beware, Watson-Guptill Publications, New York City, 1979
* R.M.Organ, Design for Scientific Conservation of Antiquities, Smithsonian Institution, Washington DC, 1968
* Thomas B. Brill, Light Its Interaction with Art and Antiquities, Plenum Press, New York City, 1980
* CRC Handbook of Chemistry and Physics, Robert Weast (ed.), CRC Press, Boca Raton, Florida, v. 61, 1980 Comment: density=3.01-3.52
Category:Materials database