WHAT IS A MINERAL
What is a Mineral?
A mineral, by definition, is any naturally occurring, inorganic substance, often additionally
characterized by an exact crystal structure.
Its chemical structure can be exact, or can
vary within limits. Native elements that occur naturally are also considered minerals.
All minerals belong to a chemical group, which represents
their affiliation with certain elements or compounds. The classified chemical groups are
known as: Elements, Sulfides, Oxides, Halides, Carbonates, Nitrates, Borates, Sulfates, Chromates, Phosphates, Arsenates, Vanadates, Tungstates, Molybdates, and Silicates. Some of these chemical groups have
sub-categories, which may be categorized in some mineral references as separate groups.
All minerals belong to one of the six crystal groups, classified according
to the way the atoms of the mineral are arranged. Minerals also have distinctive
properties, such as color, hardness, crystal habit, specific gravity, luster, fracture, and tenacity. Many of these properties can vary
among a single mineral, within limits. Many minerals exhibit certain properties that
others do not, such as fluorescence and radioactivity.
Minerals are an economic commodity; they are mined because
of the need for a valuable element they contain or an intrinsic property they may have.
Other minerals are mined for their beauty and rareness, thus giving many specimens an
accepted worldwide value. There are well over 3,000 scientifically classified different types of minerals, and new ones
are always being discovered. The vast majority are not known to professional mineral collectors,
because they are rare, have no economic purpose, and for the most part do not make good
There is a class of substances known as "mineraloids". While not truly falling into the category of minerals,
they are still usually classified as minerals. Two well-known examples are Mercury, which lacks a crystal structure due to its
liquid state, and Opal, which also lacks a crystal structure as well as a definitive chemical formula. Despite the fact that
these mineraloids lack certain essential characteristics of minerals, they are nevertheless classified as minerals in most
reference guides including the acclaimed Dana's System of Minerology. Another unique category of minerals is the organic minerals.
While this term is technically an oxymoron, since the definition of a mineral requires it to be inorganic, there are several naturally
occuring rare organic substances with a definitive chemical formula. The best known example of this is Whewellite. Most
reference guides and scientific sources make an exception to these substances and still classify them as minerals.
What is a Rock?
A rock is an
indefinite mixture of naturally occurring substances, mainly minerals. Its makeup may
vary in containment of minerals and organic
substances, and its composition is never exact. Rocks can be composed of tiny microscopic grains of minerals
or organic substances to coarse mineal agglomerates where the individual
minerals are easily discernible. Rocks may range in size from tiny pebbles to huge
mountains. Rocks make up the earth's crust.
Many rocks are not solid, such as magma, soil, and clay.
Different mineral deposits can be found in related rock
formations, providing use by estimating what minerals rock formations may contain.
The term "rock collection" is usually misused for "mineral
collection". Although a few people collect rocks, the amount of people
collecting minerals is far greater.