The Book of Crystals www.blancheofsaintandre.com !3
Chapter 1
What are crystals?
Everybody has heard of crystals. The word "Crystal" is used in
reference to a type of jewel which has a healing, spiritual or
decorative objective. Therefore, according to how the word is used,
one can assume that crystals can be used for different purposes.
But what are crystals really?
Crystals are minerals which solidify as a result of a natural
geological and chemical process. They have a unique and specific
chemical composition. They also possess extremely well-ordered
atoms and specific physical properties which are distinct for each
particular kind of crystal. Even if people call them "pretty stones",
their composition is in fact quite specific, as opposed to a
gemstone which is an agate made of minerals and/or mineraloids
(substances that have no crystallinity) but which does not have a
specific composition. The composition of a mineral can range from
pure elements of simple salts to complex silicates with thousands
of different shapes. The study of minerals is known as mineralogy.
So a crystal, in simple terms, is a mineral.
For a mineral to be classified as a "true mineral", it must have a
crystalline structure and a solid form. It must also have a
homogeneous substance which occurs naturally with a defined
chemical structure. A "crystal" possesses a geometrical spatial
arrangement of atoms within its structure. There are 14 different
three-dimensional structural arrangements of atoms known as the
"Bravais Lattice". Each of these structures can be classified in one
of the seven systems of crystals. All recognized crystals to date are
divided into one of the Bravais Lattices within one of the seven
systems.Certain gemstones are all mineral, such as limestone, which is
basically a sedimentary rock made completely of crystallised
calcium carbonate. The stones that constitute the earth's crust are
composed of quartz, feldspar, mica, chlorite, kaolin, calcite,
epidote, olivine, augite, hornblende, magnetite, hematite, limonite
and a few other minerals.
Some minerals can be commonly found all over the world, while
others are only located in specific places. More than half of the
known minerals are so rare that only a handful of samples have
been discovered and many are known thanks to one or two little
grains. Classifying minerals can range to very simple to extremely
complex. A mineral can be classified and identified by several
physical properties. Others have been identified thanks to
techniques such as X-rays. According to the International
Association of Mineralogy, which is responsible for the approval
and naming of newly discovered minerals, there are currently 4,000
known minerals. Among these, perhaps 100 could be called
"common", 50 "infrequent" and all the rest "rare" to "extremely rare