Natural Glass

Natural glass is formed naturally without the intervention of man. Its primary composition is silica with impurities. It (especially moldavite and snowflake obsidian) is used in carvings and beads.

Natural glasses are formed under different conditions and are basically made up of varying percentages of silica. The separation of natural glass from man-made glass is not possible with standard gemmological equipment. Obsidian, moldavite, crater glass and silica glass are variety of natural glass. The term Tektite has been used to represent all the natural glasses as a whole and also to define glasses of specific meteoritic origins.

Obsidian

Obsidian is really a natural glass. It is created from volcanic lava that cooled prematurely for significant crystallization to happen. Hence it's amorphous, without any cleavage; fracture is conchoidal. Obsidian is generally black, but brown, grey and much more rarely red, blue, and green material is located. The color might be uniform, striped, or spotted. Some inclusions give obsidian a metallic sheen, while internal bubbles or crystals (called crystallites) create a “snowflake” effect (hence snowflake obsidian) or an iridescence viewed as flashes of colour.

Obsidian can be found in places that there's, or may be, volcanic activity: for instance, Hawaii (USA), Japan, and Java. Other localities include Iceland, Hungary, the Lipari Islands off Italy, the first kind USSR, Mexico, Ecuador, and Guatemala. Dark nodules present in Arizona and New Mexico (USA) are known as “Apache tears”.

Obsidian has been utilized since the prehistoric era to make tools, weapons, masks, mirror, and jewellery. The sharp shards from the natural glass happen to be fashioned as blades, arrowheads, and daggers. Today most obsidian jewellery originates from North and Guatemala.

Moldavite

The very first tektites were present in 1787 within the Moldau River in Czechosolvakia, hence their original name of “moldavites”. Other colour types of this natural glass have since been present in a variety of localities. Tektites are often translucent, and happen to a variety of colours from green to brown. Their surfaces are often uneven or rough, having a distinctive lumpy, jagged, or scarred texture. Tektites don't retain the crystallites present in obsidian. They might, however, have characteristic inclusions of round or torpedo shaped bubbles or treacle like swirls.

The Moladu River in Czechoslovakia has become the only real known locality for green, transparent tektite. Tektites from Thailand happen to be carved as small, decorative objects, worn in the fact that they provide protection from evil.

Several ideas have been put forward to describe the mysterious origin of tektites. One theory is they found Earth from space, melting because they passed with the atmosphere and therefore forming their characteristic shape and surface texture.

Another theory would be that the impact of a big meteorite caused the encompassing rocks to melt and scatter, with cracks and scars then appearing because they cooled.

Crater Glass

Silica Glass

• When a lightning bolt strikes the ground, thin tubes of fused sand are formed due to intense heat build-up. Fulgarite is the name given to such fused sand glasses.
• Non-volcanic, extra terrestrial glass of meteoric origin is called a Tektite. Tektites are mostly found in Czech Republic, Australia, South-East Asia, West Africa, U.S.A. (Georgia - Texas).
• In general, all natural glasses are sometimes clubbed together as Tektites.