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Crystal Systems

There are seven different common types of crystal groups (crystal systems) and they are used to describe the “lattice” that makes up a crystal. A lattice is the three dimensional framework of atoms arranged in a symmetrical pattern and is what provides each individual un-faceted gemstone its characteristic and natural shape.
It all sounds complicated, so I’ll recall a true story which might help explain it a little better. The year was 1783; Rene Just Hauy, a 40 year old Frenchman, was about to make a big discovery. He had studied botany, but an accident was about to dramatically change his field of interest and place him in the history books of science. One evening, he slipped and dropped a large calcite crystal to the floor. It had been lent to him by a friend and as he hurried to pick up all of the shattered pieces, he noticed how all the fragments, no matter how big or small they were, all had an identical shape.

After studying these fragments in great detail, he became the first person to arrive at the conclusion that crystals are constructed by a large number of smaller units, all of which have an identical shape. He named these individual units “integrant molecules”.

From the studies initiated by Hauy, we now know that a gemstone’s outer shape is generally a reflection of its regimented internal structure. The story does not end here however. Fast forward 67 years to 1850, when another French scientist, Auguste Bravis, discovered that there were only 14 different orderly arrangements of atoms found in crystals. Later studies by Max von Laue (the German Nobel Prize winner for physics in 1914) and then the works of William Bragg demonstrated how X-rays passing through minerals would scatter in distinctive and regular patterns.

Through the work of these three gentlemen (technically it was four because William Bragg’s son was also involved in the research), today it is universally accepted that there are seven different crystal systems in which nearly all gemstones fall into: cubic; hexagonal; tetragonal; orthorhombic; trigonal; triclinic; and monoclinic.

Rubies and Sapphires, members of the Corundum family, originate from trigonal crystals. Members of the Beryl family such as Aquamarine, Morganite and Emerald are from the hexagonal crystal group. Peridot and Topaz come from the orthorhombic crystal system, and Diamond, Garnet and Spinel are members of the cubic system.

In addition to the seven crystal systems, there are a few gems that have no directional structure; these are known as “amorphous” (most dictionaries describe the word as lacking organisation or unity). Examples of amorphous gems are Amber, Jet, Moldavite and Opal.

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