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            THE CRYSTAL           University of Colorado Mineral Structure Data

        LATTICE GALLERY

Chemical Formula

• Minerals are sorted according to their chemical formula.

• The formula has 2 parts; the cation and the anion.

  • Cation - The first half of the chemical formula. It contains a positive charge is the mineral were to be dissolved.

  • Anion - The second half of the chemical formula. It contains a negative charge and what is used to categorized minerals.

  Ex - HCl - Halite (AKA salt)

  H - Cation

  Cl - Anion

   - Grouped as Chloride (due to the Chlorine anion)

Ex - KAlSi₃O₈ - Orthoclase

KAl - Cation

Si₃O₈ - Anion

 - A silicate due to Si and O group

• Most anions are more than one element (like Si and O) that form a tight bond that cannot be easily broken

• The properties of a specific mineral always remain the same because the structure of a mineral is always the same.

• Some minerals have the same formula but different structures giving the completely different properties.

Graphite (both have C as their chemical formula) Diamond

Since graphite is formed into sheets, it falls apart much more easily than diamond which is formed into an impenetrable lattice

• Many mineral properties like cleavage are also a result of the crystal structure

Halite                                     Halite Structure

The square shape of the structure causes the mineral to break off in tiny cubes (a perfect example of cleavage in 3 directions @ 90^o

Carbon structures from the Molecule of the Month page. Halite picture from The Amethyst Galleries. Halite structure picture from The Crystal Lattice Gallery

Abundance

• Most minerals are not that common, they are formed in extreme circumstances, are destroyed easily, or the building blocks for the minerals are just not present.

• Other minerals, usually the ones with the most basic structure and elements are extremely common. These can even be found in your backyard sometimes. These include:

  • Quartz

  • Feldspar - A group of minerals

  • Micas - Another group of minerals including muscovite and biotite

  • Pyroxenes - A group of minerals including augite and diopside

  • Amphibole - A group of minerals including hornblende