There are over 4800 known mineral species. As collectors we are
only concerned with a few hundred because, although beautiful, the others
require the use of powerful microscopes to view. Scientists classify minerals by
their chemical composition and related crystal structure. The most widely used
classification system is James D. Dana's System of Mineralogy.
Dana
uses 15 mineral classes: (1)native elements, (2)sulfides, arsenides, and
tellurides, (3)sulfosalts, (4)simple oxides, (5)hydroxides, (6)multiple oxides,
(7)halides, (8)carbonates, (9)borates, (10)sulfates, (11)chromates,
(12)phosphates, arsenates, and vanadates, (13)vanadium oxysalts, (14)molybdates
and tungstates, and (15)silicates. These classes can be formally divided into
families, then into groups, species, and varieties.
Since these are
our museum pages of mineral specimens and not a geology course, we will show
examples of the 8 most popular classes for collectors. Click on the pictures for
enlargement.
NATIVE ELEMENTS
Native elements are those
elements that occur in the free, uncombined state and include metallic elements
(gold, silver), semimetallic elements (arsenic, antimony), and nonmetallic
elements (carbon, sulfur).
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SULFUR | |
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COPPER | |
SULFIDES, ARSENIDES AND TELLURIDES
The sulfides
are simple compounds of one or more metallic elements or semimetals with sulfur,
a nonmetallic element. Sulfides are water-soluble and when carried far
underground with heated groundwater can result in rich deposits of copper, lead,
zinc and other metallic ores.
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GALENA | |
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PYRITE | |
SIMPLE OXIDES
The simple oxides are compounds of
metallic elements with oxygen. They are called simple oxides because of their
simple crystal structure and chemical composition. This group forms rare gems
(ruby and sapphire) and important ores.
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RUBY | |
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SAPPHIRE | |
CARBONATES
The carbonates are compounds of one or more metallic elements or semimetals with
the carbonate radical. This is one of the most popular classes with collectors.
It features some of the most beautiful minerals.
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CALCITE |
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ARAGONITE |
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MALACHITE |
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SULFATES
The sulfates are compounds of one or more metallic elements with the sulfate
radical. This is a large class of minerals with diverse properties but generally
lightly colored, soft, and fragile.
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BARITE |
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PHOSPHATES, ARSENATES, AND VANADATES
This is a large class of minerals whose metallic elements are compounded by
phosphate, arsenate, or vanadate radicals. Many are brightly colored and yield
very colorful specimens.
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VANADINITE |
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APATITE |
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LAZULITE |
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SILICATES
Silicates are the largest class of minerals. They comprise 25% of all known
mineral species (40% of the common ones) and 95% by volume of all the minerals
in the earth's crust. This group also includes some of the most valuable
minerals, investment wise, such as the Proctor Tourmaline Queen worth over a
million dollars.
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TOURMALINE |
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DIOPTASE |
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BENITOITE |
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DANBURITE |
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