In addition to being a precious gemstone, agate can be used as a polisher in industry. The colour and patterning of agate is highly variable as it is caused by the presence of  impurities. Most often it is white, milky, or grey but it can also be brown, green, red, black or combinations of all of these colours.

It is made up of silica and is therefore a member of the silicate group of minerals and gemstones. Like quartz, of which it is one of the many forms ,agate is an oxide of  metallic silicate. (Silicon is the second most abundant element in the earth's crust after oxygen

Agate is differentiated from chalcedony mainly by the different coloured bands that form across its surface. Agate is also slightly softer than chalcedony, but this difference is so small that it is almost impossible to measure with any scientifically acceptable accuracy.

Agate is porous and not very dense - it weighs just over twice the weight of an equivalent volume of water. When agate is struck with a sharp instrument, it does not break of along its structural planes (that is to say it has no cleavage), it does however fracture, and leaves behind a distinct conchoidal pattern that resembles the outside of a seashell.

Agate occurs in small rounded lumps (nodules) of volcanic lave such as basalt, where it forms in concentric or irregular layers that often line a cavity (geode)

Agate is an impure form of chalcedony. Chalcedony itself is highly impure form of quartz that forms in microscopically small crystals.

Agate is distinguished from chalcedony by its characteristic covered bands, which are caused by various impurities within the structure of the gemstone. These bands are not usually visible in the Agate specimens after first removed from the ground (many of them are concealed within large crystals of quartz), for but when the after layers are split open the revealed patterns that are sometimes beautifully concentric in form. The best of these patterns can make Agate extremely valuable as a decorative gemstone.

There are several different varieties of Agate:

Agatised wood is fossilised wood that has had its organic matter replaced by Agate

Fortification Agate has regularly arranged bands around its perimeter. These may resemble a castle viewed from the air.

Moss Agate (also known as mocha stone) is translucent and although it may colourless, it is more often white or grey in colour with dark moss like or tree like (dendritic) inclusions. These inclusions are caught by the presence of iron and manganese oxide purity is within the structure of the gemstone.

Onyx is another form of Agate with straight, parallel bands that run vertically or horizontally right across the surface of the gemstone. Onyx is very popular in pendants and broaches on which designs are cut to reveal raised figures called cameo's.

Agate is frequently cut in the slabs which are used as ornaments, or highly polished to make broaches and pendants. Because Agate absorbs liquid (is porous), is it m it may easily be dyed or stained to enhance its natural colour and increase its commercial value. If ever you see any cheaper piece of Agate and that is brightly coloured it has probably been dyed. We at Toprock think it looks awful and we are proud to NOT Stock or supply any artificially coloured Agate.

Agate is widely used as an abrasive for burnishing and polishing other materials of similar but slightly inferior hardness and also Agate is used in the manufacture of mortar and pestles which are still used by professional chemists and pharmacists.

Historically, the most famous source of Agate was at Idar-Oberstein in Germany, where gem-quality specimens were collected from at least 1548. Even though its own supplies have been exhausted, this town in the Rhineland is still the worlds leading centre for polishing and carving ornamental Agate. The raw material is now imported into Germany from the huge quartz deposits that have been discovered in Brazil and Uruguay during the last hundred years.

Other plentiful deposits of Agate have been found in China, Egypt, the Italian Alps, Madagascar and Mexico. Agate has also been found in parts of Perthshire in Scotland.

The best Moss Agate comes from the Hindustan region of India. They have also been significant Moss Agate finds in China and America. America has the most famous agatised wood in the petrified forest of Arizona.