Stone information guide - Gems and precious stones

Gems and precious stones

Gems are classified into three categories:

 precious stones, gems and ornamental stones

All the stones fall into one great family: corundum, and quartz, beryl, the chalcedony, etc..

But, in fact, what is a gem?

A rock is a natural mineral or organic (such as ivory, pearl or amber), but also a synthetic stone. It is characterized by,

• The beauty of color,

• Its relative hardness,

• Its rarity in nature.

Gems:

Everyone knows that the belly of the earth and its bark has been the scene of huge shocks of magmas under duress enormous pressure. These changes are the cause of the creation of such crystals.

Some colored crystals and especially valuable because of their rarity, have taken the "precious stones". There are four:

  

• The Diamond

• The sapphire (corundum)

• Ruby (corundum)

• The emerald (beryl)

Precious stones:

The stones, say "semi-precious" gems are transparent, which were not included in the classification of precious stones. The stones used in jewelry.

Include:

  

• Aquamarine (beryl)

• Amethyst (quartz)

• Citrine (quartz)

• Rock crystal (quartz)

• Garnet (garnet family)

• Peridot (orthorhombic crystal system)

• Topaz (crystal system orthorhombic)

• Tourmaline (family cyclosilicates - orthorhombic crystal system)

• Zircon (synthesized crystals - crystal system tetragonal)

Ornamental stones:

The ornamental stones are also called "fancy stones." They shine on their surface by the play of light. They are often cut in cabochon or used in glyptic (seals, cameos).

The ornamental stones are opaque or translucent:

  

• Agate (quartz microcrystalline - monoclinic crystal system)

• Alexandrite (chrysoberyl)

• Azurite (monoclinic crystal system)

• Chalcedony (quartz family which include chalcedony)

• Cornelian (quartz)

• Hematite (rhombohedra crystal system)

• Jade (for the family of pyroxenes jadeite and nephrite amphibole)

• Jet (variety of lignite)

• The jasper (quartz - crystal system monoclinic)

• Lapis lazuli (for the crystal system cubic lazurite)

• Malachite (monoclinic crystal system)

• marcasite (orthorhombic polymorph)

• Obsidian (glassy rock fluidal texture)

• Onyx (chalcedony)

• Opal (amorphous crystal system)

• The moonstone (feldspar family)

• Sardonic (chalcedony)

• Turquoise (family phosphates)

  

Organic substances:

 • Coral

• Pearl

• Amber

We have chosen to present below many gems by ordering as much as possible according to their relationship when they exist.

First of all gemstones, diamond is the subject of a separate chapter, followed by other materials:

• Sapphire

• Ruby

• Emerald

• Beryl

• Aquamarine

• Amethyst

• Citrine

• Jade

• Quartz

• Onyx

• Garnet

• Peridot

• Topaz

• Tourmaline

• Kunzite

• Opal

• Spinel

• Pearl

• Coral

• Amber