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Glass or Paste
Glass or Paste

Glass as a Gemstone
It may seem strange to describe glass as a gemstone. There is no reason to exclude artificial materials from any list of gemstones. If something is used as a gemstone, then it is valid to treat it as such, while bearing in mind that it is an artificial simulant rather than a natural object.

Natural Glass
Just to confuse matters, there are a number of natural glasses such as obsidian, which can be classified accurately and undisputably as a gemstone. Natural glasses can originate from volcanoes or meteorites.

Synthetic Glass Gems or Paste
When glass is used as a gemstone simulant it is known as paste. The ancient Egyptians used coloured glass as gemstones, and it is still used today in costume and fashion jewellery as an inexpensive but reasonably effective imitation for more expensive gemstones. Paste stones are often foil backed to reflect more light, the foil sometimes being coloured. Other reflective coating have been used including mercury amalgam in Bohemian paste stones.

Colours of Glass
By "doping" with different minerals, many different and attractive colours can be produced. The best known, and commonest is colourless, usually referred to as white.
Cerium oxides, CeO2, Ce2O3, produce red orange and yellow.
Copper, CuO, Iron, Fe2O3, Nickel, NiO, Praesiodymium, Pr2O3, and Titanium, TiO2, oxides all produce yellow amber and brown.
Erbium, Er2O3, Europium, Eu2O3, Holmium, Ho2O3, oxides produce pink.
Chromium, Cr2O3, Thulium, Tm2O3, Vanadium, V2O3, oxides produce olive green.
Cobalt, Co2O3, Manganese, MnO2, Neodymium, Nd2O3, oxides all produce lilac and violet.

Technical Information
Common glass is made from sodium silicate, but a large variety of silicates can be used. Other additions give rise to many specialised glasses.
Chemical Composition and NameSiO2 - Silicon Dioxide
Hardnessusually less than 6
Refractive Index1.44 - 1.90
Specific Gravity2 - 6
Crystalline System the Lowest Possible Price

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