Perhaps the best known form of silica is glass. When molten silica cools rapidly, it doesn’t have time to align into a well organized structure (crystals) and stays in a higgledy-piggledy disorganized (albeit extremely viscous) liquid. This may occur in nature via  several mechanisms.


Rainbow Obsidian

Rainbow Obsidian

Rainbow Obsidian 2

Rainbow Obsidian 2

Rainbow Obsidian 2 under the microscope

Rainbow Obsidian 2 under the microscope

gold sheen obsidian

Gold sheen obsidian

spider obsidian

Spider obsidian

mahogany obsidian

Mahogany obsidian.

Here layers of different oxides of iron have formed layers, and it is easy to imaging hot flowing lava stretching, deforming and twisting these layers as they flowed from the magma chamber onto the earth’s crust.
snowflake obsidian

Snowflake obsidian

As the molten glass cooled , sometimes at higher temperatures (600+°C there was time, in areas of the glass, for cristobalite to crystalize out. This is a white opaque polymorph of silicia which produces radial crystals, reminiscent of snowflakes.


The instant before a meteorite hit the earth, there is a huge increase in pressure and temperature. The underlying material is melted and expelled high into the atmosphere (up to 20 km, where the temperature is around -50°C. Rapid cooling occurs and “blobs” of glass solidify out and fall to the ground. They are known as tektites
Vietnam tektite

Vietnam tektite



This beautiful green glass is found only in the area of Moldova. The green colour is given by the presence of ions of chromium.


When lightning strikes a tree or plant the energy is transferred down through the stems to the roots. The temperature in the surround few millimetres can reach 36,000°C, vapourizing all surrounding material. A the soil cools and solidifies a “dirty” glass is formed- fulverite.


The path of the lightning strike is along the root, giving this characteristic shape. The root itself  was instantaneously vapourized and only a hollow core indicating its original presence is left.
Man Made Glass Man has made use of the properties of glass in multiple ways, windows, plates, drinking glasses, spectacles and objet D’art.

A Bambi

This is one example of Venetian glass, produced on the island of Murano for over 800 years.

A selection of glass on sale in a shop in Prague.

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