Oyster muscle shells teeth crystal o single

Oyster / muscle shells
 Teeth
Crystal
o Single, continuous, piece of crystalline solid
o Bound by flat surfaces (crystal faces) with regular geometric form occurring naturally
o Consistency of interfacial angles
o The same mineral has the same crystal faces and angles between them
o Crystal examples:
o Diamond, quartz, garnet, etc.
o Crystals interact with light to create attractive beauty
o X-Ray Diffraction (XRD) proposed by Max van Laue is still used to look inside crystals
o The order of the atoms in a crystal repeat regularly in three dimensions
o This is called Crystal Lattice
o The order of these atoms display symmetry, and this order defines the crystal structure
o Physical properties of crystal depend on:
o Identity of atoms
o Arrangement of atoms
o Nature of atomic bonds
o Diamond and graphite are made entirely of Carbon
o Diamond - atoms are arranged in tetrahedral (hardest mineral)
o Graphite – atoms arranged in sheets; softest mineral
o Polymorph – same composition, different structure
Mineral Formation
o New crystals form in 5 different ways:
o Solidification from a melt
o Crystals grow when the melt cools
o Liquid freezes to form solid
o Precipitation from solution
o Seeds form when precipitation becomes saturated

o Solid State diffusion
o Garnets
o Biomineralization
o Our tooth enamel is mineral apatite
o Precipitating from Gas
o Tiny early crystal acts as seed for growth
o Atoms migrate to seed and attach
o Growth moves face outward from center
o Sometimes if crystals grow in confined spaces, they don’t have faces, as the faces are obstructed by objects
around the crystal
o Anhedral – grown in tight space, no faces
o Euhedral – grown in open cavity, good faces
Mineral Destruction
o Minerals can be destroyed by:
o Melting – heat breaks the bonds holding atoms together
o Dissolving – solvents break atomic bonds
o Chemical reaction – reactive materials break bonds
Mineral Physical Properties:
o Color
o Streak
o Color of powder produced from crushing a mineral
o Luster
o The way mineral surface scatters light, metallic, or non-metallic
o Hardness
o Scratching resistance
o Derives from strength of atomic bonds
o Specific gravity
o Density of mineral
o How heavy it feels
o Crystal habit
o Shape characteristics
o Is it a single crystal with well-formed faces, an aggregate of many well-formed crystals
o Records variation in directional growth
 Block = same speed growth in all directions
 Needle-like = fast growth in only one direction
o Fracture or cleavage
o Minerals break in ways that reflect their atomic bonds
o Fracturing implies equal bond strength in all directions
o Cleavage – tendancy to break along planes of weaker atomic bonds
 Produces flat, shiny surfaces
 Cleavage is all through the crystal, usually produces parallel steps, where crystal faces only occur
on external faces
Mineral Classification
o Minerals can be broken into a few groups. J. J. Berzelius, a Swedish chemist, noted similarities
o Minerals can be separated by:
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