Garnet

When you think of a garnet, you may think of a deep-red colored gem. However, not all garnets are red. There are many different types of garnets and they can be any color or even colorless. Garnets range from the gemstone-quality transparent specimens, to the opaque varieties used for industrial purposes.

Garnets are opaque, transparent to translucent minerals that can be found as individual crystals, pebbles, or clumps of inter-grown crystals. Garnets are most commonly found with reddish shades, but can be, orange, yellow, green, purple, brown, blue, black, pink, and colorless. Blue garnets are very rare. Sometimes the crystals have alternating layers of lighter and darker colors. Garnets with inclusions can have a star-shaped pattern of reflections or appear to change colour under different types of lighting. Almandine garnets are the most common and are frequently used as a gem. Garnet crystals nearly 1 metre in dimeter have been reported from Gore mountain garnet mine in USA.

Uses
Garnets have been used since the Bronze Age as gemstones for jewelry and ornaments and as abrasives. Because garnet is so hard and resistant to weathering, it can be used as skid-resistant road aggregate, skid resistant paints, and for filler in concrete being used in harsh environments.

Garnets are used for industrial blast-cleaning, polishing, filtration and water jet cutting. A waterjet cutter produces a high-pressure jet of water with garnet and other abrasive grains in it. When the jet is aimed at a piece of metal, ceramic, or stone, it cuts the material producing very little dust. Garnet is starting to replace silica in abrasives, because silica is dangerous to workers health. Silica has been linked to a disease called silicosis.

More recently, lithium- oxide garnets have been receiving a lot of interest from researchers, because they can be used as electrolytes for batteries. Garnet crystals with a large number of lithium atoms in the crystal structure are called lithium-stuffed garnets, and these have been used in rechargeable battery technologies.

History
Garnet gemstones have been favoured by the rich and famous for many centuries. They have been found in many ancient Greek, Roman and Egyptian ruins. Red garnet necklaces were found in the tombs of Egyptian pharaohs, dating back to 3100 BCE and Ancient Romans were known to use carved garnets in signet rings to stamp wax seals, on important documents.

During the middle-ages (300 to 900 BCE), jewelers, in Scandinavia and Asia, used a technique called Cloisonné to decorate metal objects. The decorations consisted of compartments, with fine walls of silver or gold, filled with inlays of cut garnet and rhodolite gemstones, glass or other materials. The objects, known as cloisonnés were valued by royalty and those in power.

In 2009 a large collection of metal artefacts decorated with gems, including garnets, was found on farmland in Staffordshire, England, by a man using a metal detector. The 3500 items, referred to as the Staffordshire hoard, were manufactured during the 6th and 7th centuries and included weapons, religious artefacts and jewellery.

In the 14th century, pyrope-garnet deposits were found in the area now known as the Czech Republic, and the gem cutting industry thrived there until the 19th century.

Garnets have featured in a range of folklore and legends. In the Talmudic version of Noah’s Ark, the ark was lit up by a massive red garnet and in the middle ages, garnets were sought after as a cure for depression. In northern Pakistan between 1889 and 1892, the Hunzas used garnet bullets to fight the British. They believed that garnets would be more effective bullets than lead because they were red, like blood.