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In mythology, legend and tradition, minerals have various symbolic
values. Supernatural powers have been ascribed to some minerals. Precious gems
are common symbols of wealth or royalty. Thus, the expression crown jewels.
Specific gems or minerals are commonly associated with some nations. For
example, diamonds are often linked to South Africa, where they are so common.
Turquoise is commonly associated with Persia (Iran).
However, few nations have officially adopted rocks or minerals as symbols,
though they are sometimes depicted on flags or coats of arms. The color yellow
represents mineral wealth on some national flags and arms.
In contrast, such symbols are extremely popular among the fifty U.S. states.
Several provinces, territories and states in Canada and Australia have also
adopted mineral symbols.
Classification
Minerals can be divided into
ten classes, seven of which (in black type)
are represented among state and provincial geosymbols: |
Elements
Sulfides
Halides |
Oxides
Carbonates
Sulfates |
Phosphates
Silicates |
Organics
Mineraloids |
The chart below lists all minerals adopted as official geosymbols. Some
minerals have been adopted by more than one jurisdiction. For example,
gold is an official symbol of Alaska, California, South Dakota and the
Northwest Territories. |
Native Elements
The Native Elements Class includes more than 100 minerals divided into
three groups. |
Subclass: Native Non-metals
and Semi-metals
This is the most diverse group and includes the hardest known mineral (diamond)
as well as one of the softest.
Carbon Group:
Diamond C |
Subclass: Native Metals
Metals are distinguished largely by their colors. The gold group and iron
are among the most valuable minerals, including mercury (Hg),
which is not a state symbol.
Gold Group:
Copper Cu
Gold Au
Lead Pb
Silver Ag
Iron Fe
(Other familiar metals include aluminum, cadmium, chromium, nickel, platinum,
tin, titanium and zinc.) |
Subclass Metallic Alloys
(Brass (Cu3Zn2) is a well known member of this group, though
it has not been adopted as a state symbol.) |
Sulfides
The members of the Sulfide Class form an economically important class of
minerals. Important metals such as silver, copper, and lead are usually
found in sulfide ores. Most sulfides are metallic, opaque, and soft to
average in hardness. Most are igneous in origin.
The Standard Sulfides:
*These minerals are sometimes thought of as alloys of metals with semi-metals
and placed in the Elements Class. Galena (Lead
Sulfide) |
Halides
Halides (Halogens) that are found commonly in nature include Fluorine,
Chlorine, Iodine and Bromine. The best known halide mineral is halite
(NaCl), or rock salt. Fluorite (Calcium Fluoride) |
Sulfates
Included in this class are various subclasses: the Sulfites, the Chromates,
the Molybdenates, the Selenates and Selenites, the Tellurates and Tellurites
and the Tungstates.
Although many minerals belong to this class only barite, gypsum, and anhydrite
can be considered common.
The typical Sulfate Class mineral is vitreous, average to above average
in density,average in hardness and are originally formed in veins, oxidation
zones,contact metamorphic zones and in evaporite deposits. Some Sulfate
Class minerals are soluble and several are fluorescent.All other properties
are variable.
Subclass: Sulfates
The Barite Group:
Barite(Barium Sulfate) |
Phosphates
The Phosphate Class includes one state/provincial symbol, lazulite (Magnesium
Iron Aluminum Phosphate Hydroxide), which belongs to the subclass Phosphates.
(The other subclasses are the Unanyl Phosphates, Arsenates, Antimonates,
and Vanadates.)
Subclass Phosphates
Lazulite (Magnesium Iron Aluminum Phosphate Hydroxide)
Turquoise (Hydrated Copper Aluminum Phosphate Hydroxide) |
Silicates
Some geologists estimate that 90% of the Earth’s crust is made up
of silicates, which constitute 30% of all minerals! Why are they so common?
Most silicates are made of oxygen and silicon, the two most abundant elements
in the earth’s crust.
The Silicates are divided into the following subclasses by their structures:
Nesosilicates (single tetrahedrons)
Sorosilicates (double tetrahedrons)*
Inosilicates (single and double chains) |
Cyclosilicates (rings)
Phyllosilicates (sheets)
Tectosilicates (frameworks) |
| *No state symbols are found
within the Sorosilicates. |
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The Nesosilicate Subclass
Nesosilicates are exceptionally hard and include more gemstones than any
other silicate subclass. Below are the more common members of the nesosilicates.
See the nesosilicates’ page for a more complete list.
The Garnet Group:
Almandine (Iron Aluminum Silicate)
Grossular (Calcium Aluminum Silicate)
Sillimanite (Aluminum Silicate)
Staurolite (Iron Magnesium Zinc Aluminum Silicate Hydroxide)
Topaz (Aluminum Silicate Fluoride Hydroxide) |
The Inosilicate Subclass
The Pyroxene Group:
Jadeite (Sodium Aluminum Iron Silicate)
Rhodonite (Manganese Iron Magnesium Calcium Silicate)
Babingtonite (Calcium Iron Manganese Silicate Hydroxide) |
The Cyclosilicate Subclass
There are several gemstone minerals represented in this group, a testament
to the general high hardness, luster and durability.
Benitoite (Barium Titanium Silicate)
Beryl (Berylium Aluminum Silicate) [Includes Aquamarines & Emeralds]
The Tourmaline Group |
The Phyllosilicate Subclass
Minerals in this group tend to be flat and platy. It includes such unusually
soft minerals as talc, which is used in talcum powder.
The Clay Group:
Talc (Magnesium Silicate Hydroxide)
Serpentine (Iron Magnesium Silicate Hydroxide) |
The Tectosilicate Subclass
Many Tectosilicates are made up largely of silicon and oxygen. The near
pure of only silicon and oxygen is quartz (SiO2).
The Feldspar Group:
Labradorite (Sodium Calcium Aluminum Silicate)
The Quartz Group: (All Silicon Dioxide)
Quartz
The Zeolite Group:
Stilbite (Hydrated Sodium Calcium Aluminum Silicate) |
Mineraloids
The members of this unofficial class are often mistaken for minerals, but
lack the necessary crystalline structure to be classified as such. They
are found naturally, are often treated as gemstones, and are included in
most mineral references (which is why we decided to include them here!).
(Note: Some mineralogists place opal in the quartz group.)
Amber (Succinite - fossilized tree resin)
lechatelierite (Nearly Pure Silica Glass)
Obsidian (Volcanic Silica Glass)
Opal (Hydrated Silica)
Tektites (Meteoritic Silica Glass) |
| Are you wondering why limestone and marble aren’t
listed above? They’re rocks, not minerals. Limestone and marble are
made of fossilized animals, as is agatized coral. Limestone is a sedimentary
rock which turns into a harder metamorphic rock called marble when placed
under enough pressure. Similarly, coal is composed of
fossilized plant remains. |
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