### crystal:

Larger crystal
* enclose small crystals.
* mean fewer grain boundaries that lower the thermal conductivity.
* show hexagonal prismatic and pyramidal forms.
* tend to grow at the expense of smaller ones.

Optical crystal
* controls properties.
* is flawless and as clear as prescription eyeglasses.

Perfect crystal
* All perfect crystals have flat surfaces.
* are essential components for advanced neutron optics.
* show translational symmetry which allows the application of group theory.

Photonic crystal
* are materials that can guide light losslessly.
* are structures with a periodic variation of refractive index
  - spatial periodicity in the dielectric function
* function in visible spectrum.
* is crystal.

Piezoelectric crystal
* force ink through the nozzles onto the paper.
* lack a center of symmetry.

Protein crystal
* are one type
  - soft and very fragile
  - usually very small, often only the width of a human hair
  - very fragile, soft, and sensitive to environmental variations
* contain water, some of which is firmly bound to the protein surface.
* form inside a lipid crystal.

### crystal:

Quartz crystal
* amplifies communication between humans and animals, and strengthens mental clarity.
* are a gift from the earth
  - abundant in vugs at both outcrops
  - more complex and are formed of silicon dioxide molecules
  - usually hexagonal and prismatic, and often twinned
* are, in all reality, only 'tools'.
* can also provide oscillations that can be used to drive clocks.
* come in many different sizes.
* exist in a number of varieties.
* have electro-magnetic properties, hence their use in a lot of electrical devices
  - excellent healing properties
  - many physical properties
* is of course a gemstone that is found in the ground
  - quartz
  - scattered worldwide as one of the earth's most abundant minerals
  - the best material for frequency-control oscillators
* keep radio signals from wandering.
* radiates a white healing light.

Rock crystal
* colorless form of quartz occurring in distinct crystals.
* is colorless
  - much less common, although in places it is very abundant
  - one of the hardest materials to carve
  - only one of several quartz varieties
* is the clear variety that is also used as a gemstone
  - purest form of quartz and a semi-precious stone

### crystal:

Salt crystal
* are abrasive and corrosive
  - in cubic form and are referred to as cubic packing of almost equal spheres
* are often visible and tasteable on the back of the leaves
  - the underside of the leaves
  - some of the easiest to grow
  - unexpectedly square
* dissolve on the surface of the cheese creating a brine that is absorbed by the curd.
* expand, pushing the crust of salt into rough, chaotic forms.
* taken up by the roots are stored in the leaves.
* tend to absorb moisture from the air.

Single crystal
* do thus deform by glide in the m direction.
* is the dominating method used for structural elucidation.

Small crystal
* evolve into large crystals.
* form at temperatures slightly below the freezing point of the fruit
  - in cool syrups that are constantly stirred

Smaller crystal
* give off blue light, larger ones green or even red.
* result in less chemical segregation and higher mass physical properties.

Snow crystal
* All snow crystals are hexagonal.
* are always six-sided because of the way water fits together as it freezes
  - one of the most popular natural products
  - the hieroglyphs sent from the sky
* can last an instant and melt.
* form by a process of sublimation.
* formed in the clouds can have a variety of shapes, depending on the temperature.