Mineralogy & Gemology

Mineral

A naturally occurring, inorganic solid with a crystalline structure with a definite chemical composition

Rock

A naturally occurring solid aggregate of one or more minerals, mineraloids, or organic material

Gem

A mineral with human intervention ex, cutting, polishing, faceting. Can also be an organic material

A mineraloid

Similar to a mineral but doesn't have the same chemical structure as minerals

Gem Formation Factors

temperature, pressure, chemical ingredients, time

Crystal Growth process

hydrothermal solution freezing

Hydrothermal solution

Water flows under the earth in high heat and pressure dissolving minerals to create a mineral rich liquid

Igneous Extrusive Rocks

forms from molten rock above ground, not giving enough time for crystals to form

Igneous Intrusive Rocks

forms from molten rock underground, giving time for crystals to form. Erosion often brings these rocks to the surface

Sedimentary Rocks

from from eroded fragments of other rocks combined into a different rock with heat and pressure

Metamorphic Rocks

When preexisting rocks change into something else due to heat and pressure

Atomic Structure

subatomic particles, atoms, elements, matter

Element

The smallest pure substance

protons

The number of BLANK in the nucleus determines which element an atom is.

electrons

The number of BLANK surrounding the nucleus determines which kind of reactions the atom will undergo AND govern the bonds of minerals

Ionic Bonds

Atoms held together by exchange of electrons

Covalent Bonds

Atoms sharing electrons

Metallic Bonds

Electrons are not tied to any one atom

Van der Walls interactions

Very weak bonds between layers of atoms

Small to Big structure

Bonding ↓ Atomic arrangement ↓ Crystal structure ↓ Physical properties

Coordination Number

the number of atoms or ions immediately surrounding a central atom or ion

Direct relationship between ions size and strength

a larger central ion can accommodate more neighboring ions around it.

Silicon (Si)

the second most abundant element on earth

Oxygen (O)

the most abundant element on earth

Silicate

a chemical compound containing silicon, oxygen, and one or more metal ions

Nesosilicates

single tetrahedra

Sorosilicates

Paried tetrahedron

Cyclosilicates

rings

Inosilicates

single chains or double chains

Phyllosilicates

sheets

Tectosilicates

frameworks

Silicate Mineral

major structural groups based on how their basic silicon-oxygen tetrahedra (SiO4) are linked together

silicate arrangement strength

More bonds make a material stronger

Crystal Structure

The order of repeating arrangement atoms

Crystal System

Classification based on symmetry of the unit cell

Crystal Habit

The external characteristics of a crystal

Polymorph

minerals that have the same chemical formation but are arranged differently making them different minerals

Cubic, Tetragonal, Hexagonal

3 important crystal lattice systems

tetrahedron

the connectivity pattern
(structural scale)
• Not just one tetrahedron, but a repeating motif of tetrahedral connections

Unit cell

the smallest repeatable 3D package (crystallographic scale)

• Contains the tetrahedra (and other atoms) arranged in the correct pattern

• When repeated in space, it creates a crystal

Cubic (isometric)

All three axes are equal in length, and all are perpendicular to one another

Trigonal

All three axes are of equal length, and none of the axes is perpendicular to another, but the crystal faces all have the same size and shape

Hexagonal

Of four axes, three are of equal length, are separated by equal angles, and lie in the same plane. The fourth is perpendicular to the plane of the other three axes