Mica is a hydrous potassium, aluminum silicate mineral with sheet structure. Only 6 common rock-forming mica species exist, including muscovite and biotite. All micas except glauconite show perfect cleavage into flexible sheets. Glauconite occurs as green pellets with no visible cleavage
Crystal is a solid with atoms arranged in definite pattern. Solids must maintain shape longer than viscous fluids. Basic units are atoms or molecules with electron shells
Miller indices are a 3D coordinate system for crystals based on unit cell. Origin is typically defined as back left corner of crystal. Scale is unit cell size, with 0 being origin of one cell. Negative values written as "bar" instead of "-"
Ionic bonding involves electrostatic attraction between oppositely charged ions. Metals lose electrons to form cations, nonmetals gain electrons to form anions. All ionic compounds have some degree of covalent bonding. Bonding occurs when ionic character exceeds covalent character
Elements are divided into metals, metalloids and nonmetals based on shared properties. Metals are shiny, good conductors, form alloys and have basic oxides. Metalloids are metallic-looking, semiconductors with amphoteric oxides. Nonmetals are dull, poor conductors, form acidic oxides
An octahedron is a polyhedron with eight faces. Regular octahedron is a Platonic solid with eight equilateral triangles. Regular octahedron is convex and has dihedral angle of 109.47°. Regular octahedron's volume is twice that of a square pyramid