Specimens

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 this is an introduction to mineral collecting and not a geology course, we will show the 8 most popular classes for collectors:

SULFUR

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). The specimen at the left is a sample of Sulfur from the El Desierto Mine, Bolivia.

PYRITE

SULFIDES - 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. The specimen at the left is a sample of a Pyrite cube from La Riosa, Spain.

CORUNDUM

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. The specimen at the left is that of corundum which in its crystal state is a ruby or sapphire depending on color. It was found in the Ural Mountains of Russia.

FLUORITE

HALIDES - Halides are minerals in which a halogen element (bromine, chlorine, fluorine, or iodine) is the only anion (negatively charged ion). This class features the fluorites which is a favorite among collectors. The specimen at the left is a Fluorite from the Minerva Mine, Hardin County, Illinois.

RHODO-
CHROSITE

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. The specimen at the left is of red Rhodochrosite with Quartz and Pyrite from the Sweet Home Mine, Alma, Colorado.

CELESTITE

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. The specimen at the left is a geode of Celestite crystals from the Malagasy Republic, Madagascar.

APATITE

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. The specimen at the left is an Apatite crystal from Siberia, Russia.

BENITOITE

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. The specimen at the left is of Benitoite crystals on Crossite from the Benitoite Gem Mine, Benito County, California. Its value is placed at several thousand dollars as well.