The Gallery of Minerals
The Gallery of Minerals
Minerals are very important. We study them because they play a major role in our economy,
industry, and health. We use hundreds of products every day that are made up of them.
The following are examples of common minerals that are categorized by type. Each has a
thumbnail picture of the specimen and a brief description of it. Clicking on the name of the
individual specimen will take you to a page with a larger picture and a detailed description.
But before we get to individual specimens lets see if we can agree on what these things are.
A scientific definition says that it is something that:

occurs naturally.

Is solid at room temperatures

has a regular structure (its atoms have a definite arrangement).

Has a chemical formula
There are a few things that don’t seem to fit even though they seem to belong. See
mineraloids.
The Silicates
Amazonite is a beautiful green variety of microcline feldspar. Its
chemical formula is KAlSi3O8 , potassium aluminum silicate.
The Gallery of Minerals
Tanzanite is a variety of Zoisite. It is valued as a gem stone and
has the chemical formula Ca2Al3Si3O12(OH).
The Mica Group is the name given to a group of silicate minerals
that have silicon and oxygen as their two major components.
Muscovite is a member of the mica mineral group. It is more
important as a rock-forming mineral than as a collectible
specimen.
Biotite Biotite is a member of the mica branch of the silicate
mineral group. It is common as a rock-forming mineral and is
present in all three rock types: igneous, metamorphic, and
sedimentary.
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Sodalite is a deep royal blue silicate. The deep color and the fact
that it will take a high polish makes it popular in jewelry and
other decorative items. The chemical formula is Na8Al6Si6O24Cl2.
Topaz is a silicate mineral that can be many different colors.
The fact that it will take a high polish and is very hard makes it
popular in jewelry. The chemical formula is Al2SiO4(F,OH)2.
Talc is a metamorphic mineral from the silicate family. Its
chemical formula is hydrated magnesium silicate H2Mg3(SiO3)4.
Talc is commonly used as talcum powderto reduce friction,
promote dry skin, and prevent rashes.
The Quartz Family
Quartz is one of the most common of all minerals that make up
the continental crust. It is found in igneous, metamorphic, and
sedimentary rocks. It is associated with many valuable ore
deposits as well.
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Amethyst is a variety of quartz and owes its purple color to the
presence of iron. It is composed of silicone dioxide SiO2.
Agate is the name given to a group of silicates that are made up
primarily of chalcedony. Chalcedony is a member of the quartz
family of minerals. Like quartz chalcedony is silicone dioxide
with a chemical formula of SiO2.
Tigers Eye is a form of quartz with some special characteristics.
Like all quartz it is made up primarily of silicone dioxide, SiO2.
Within this matrix are asbestos fibers usually occurring in
layers. It is the asbestos that makes Tiger eye a chatoyant
gemstone.
The Sulfates
barite is a sulfate mineral with a chemical formula of BaSO4,
sometimes called heavy spar. Its chemical name is barium
sulfate. It is the primary source of the element barium.
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Celestite is made up of strontium sulfate. The chemical formula
is SrSO4. Its name comes from Latin, caelestis meaning celestial.
selenite Selenite is a very common chemical sedimentary
mineral. Its chemical formula is Calcium Sulfate dihydrate
CaSO42H20, It is a form of gypsum. It is a very soft mineral.
The carbonates
Rhodochrosite is a manganese carbonate mineral. Its chemical
composition is MnCO3. In its purest form it is a transparent rose
red, but this is fairly rare. It can also be formed in stalactites.
This form can be sliced revealing circular layers of rose and pink
to milky white. These lighter colors are formed when the
manganese is replaced by calcium, manganese or zinc. The
depth of color from red to pink depends on the amount of
substitution.
Azurite is a copper carbonate. The chemical formula is Cu3[OH
CO3]2and results from the oxidation of copper sulfides.
The Gallery of Minerals
Malachite is a copper carbonate with a chemical formula of
Cu2[(OH)2 CO3]. It is a vibrant green color often banded with
light and dark greens.
Calcite Calcite is a very common sedimentary mineral. It has the
chemical formula CaCO3 calcium carbonate. Calcite dissolves in
water and so is carried along with water into cracks, fissures,
and caves. It can over time build up layer upon layer to form
stalactites and stalagmites in caves.
The Oxides
Magnetite is sometimes called lodestone. It is strongly
magnetic. It was used by the ancient Chinese to make the first
magnetic compasses. The chemical formula is Fe3O4.
Hematite is one of the most prevalent and useful forms of iron
on our planet. It is a common iron ore and is often used in
jewelry and other decorative items. The chemical formula is
Fe2O3.
The Halides
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Halite Halite is also known as rock salt. The chemical name is
sodium chloride NaCl It is called an evaporate. It forms in places
where sea water has been isolated from the ocean forming a
lake.
Fluorite Fluorite is a halide that is soft and usually colorless but
can be blue, purple, green, brown, or yellow. Some times several
colors are present in the same crystal creating a striking affect.
The Sulfides
Galena has been mined for lead and silver since the time of the
Romans. It is a form of lead sulfide. The chemical formula is
PbS. It is the most important source of lead and is abundant and
widespread in occurance.
Stibnite Stibnite is a sulfide found in low temperature
hydrothermal veins and hot springs deposits. It is prized by
collectors for the long slender bladed crystals. These can occur
in clumps with many orthorhombic crystals radiating in all
directions. It is very soft only a 2 on the Mohs hardness scale.
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Pyrite sometimes called iron pyrite is a compound of iron and
sulfur, iron sulfide FeS2. Depending upon the conditions under
which it forms pyrite can form crystals of different shapes.
Phosphates
Apatite is the name given to a group of phosphate minerals that
are widely distributed in all rock types, usually in tiny crystals
spread throughout the host rock. It is usually green in color.
Turquoise is classed as a phosphate mineral. The chemical
formula is CuAl6(PO4)4(OH)8 4H2O a hydrous phosphate of
copper and Aluminum.
The Elements
Gold is a soft metallic element. Its symbol is Au. It is very dense.
As one of the noble metals it is resistant to corrosion and
oxidation in moist air.
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Copper is a soft metallic element. Its symbol is Cu. Native
copper is rare because it has been mined for centuries. Today it
is used for making wire, tubing, and coins to name a few. Long
ago it was combined with tin to create bronze.
Bismuth Crystals Bismuth in its elemental form is a rare
occurance in nature, even more so for bismuth crystals. Lab
grown crystals are popular because of their intricate shapes and
dazzaling colors.
Silicon Silicon is a metallic element used to make computer
chips and other electronic equipment. Although it is the second
most abundant element in the world it was not discovered until
1824.
The Mineraloids
Mineraloid is the term used for those substances that do not fit
neatly into one of these eight classes. Opal, jet, amber, and
mother of pearl all belong to the minera