What kind of rock is sapphire

Sapphire's companion variety of corundum is ruby. Rubies are red to orange-red to purplish red. If corundum is pink, the United States Federal Trade Commission requires that the stone be sold as a sapphire. In the United States "pink rubies" are eliminated from the gem trade by legal definition.

In the simplest terms, corundum that is any color other than red is a sapphire. Except for color, all of the other physical and optical properties of sapphire are identical to those of ruby and you are referred to the ruby page for these data. Supply and demand has dictated that cornflower blue sapphires are the most expensive. These stones are rare and the finest examples come from Kashmir, a mountainous area in northern India on the Pakistan border. Geographic isolation, political instability and high demand all combines to make these stones very expensive.

Sapphires have been found in many other places in the world but few have attained the desirability of the Kashmir stones. In the United States, the Yogo Gulch area in Montana has historically produced some fine sapphires but few of these attain the size of the fine Kashmir gems.

Labor and mining costs have been very high in the United States and the Yogo Gulch mines have generally not been profitable for the operators. Fee localities are areas where one can pay a set fee for the privilege to extract gems and minerals from mines or claims that are owned by a second party. There are several such fee locality sapphire mines in Montana that have been profitable for both the mine owners and the prospectors who have chosen to pay the fee.

The prospector pays a set fee for the right to extract a given weight or volume of sapphire bearing rock or gravel. The fee locality operators allow only the use of hand tools such as picks, shovels, crowbars, gads and wedges. But we do know that the sapphires which are found today were formed around to million years ago. Today the modern location of rubies and sapphires gives us some clues and indications about the place of their formation.

The main deposits of high quality sapphires and rubies are found only in a few places, mainly southern Asia and eastern Africa and the islands of Sri Lanka Ceylon and Madagascar.

The answer as to what took place inside the earth to form these gems and then transport them to the surface varies from country to country, but the story remains the same. Later the moving crustal plates and erupting volcanoes carried these rocks to the surface. As a result, the Russian crown jewels and lots of jewellery belonging to Russian Nobility contain gems from Australia. After the Russian revolution in , there was a downturn in the sapphire industry and few miners remained in the Australian sapphire fields.

In , the Queensland government set aside land for the use of small sapphire miners, prospectors and gem collectors, because of an increase in interest from tourists and gem buyers, mostly from Thailand. The s also saw an increase in mining using heavy machinery, leading to a small mining boom in the Queensland sapphire fields.

This lasted until sapphire prices fell in the late s. Star of India. One of the most famous sapphires, is the blue sapphire given to Princess Diana in her engagement ring, now worn by Kate Middleton.

However, there are other famous sapphires belonging to the royal family. The Stuart Sapphire is a large oval-shaped carat Edward's Sapphire, is also located at the top of the crown along with 15 other sapphires.

The Star of India, at carats, It was discovered more than years ago in Sri Lanka, but formed about 2 billion years ago. Valuable sapphires are still found in Sri Lankan deposits of sand and gravel left by ancient rivers. Industrialist and financier J. Black Star of Queensland. Sometimes sapphires can have bands of colour in them. The 85 carat 17g Tomahawk Tiger, found at Tomahawk creek in Queensland is a yellow sapphire with blue bands.

The most famous Australian sapphire is the Black Star of Queensland. It is a carat The crystal was discovered by a 12 year old boy in the s near Anakie Queensland.

The boy's family used it as a doorstop in their home for over a decade, before they realised the value of the stone. Corundum, sapphire and ruby forms deep in the Earth's crust and is brought to the surface in igneous rocks that are high in aluminium but low in silicon, such as basalts. Corundum is also found in rocks that have been metamorphosed. The basaltic, volcanic rocks in Eastern Australia are a major source of corundum, sapphire and ruby, however, the minerals are rare and not commonly mined directly from these rocks.

This is because it is very expensive to extract small gems from hard rock and many of them are broken during mining. Economic sapphire and ruby deposits are only found when an igneous rock, such as basalt, is weathered and eroded away, leaving behind the tougher and more resistant minerals such as sapphires and rubies. These then become concentrated in certain parts of the landscape after being transported by rivers and streams placer deposits.

Most of the sapphires and rubies from eastern Australia occur in placer deposits. Neal Litherland is an author, blogger and occasional ghostwriter. His experience includes comics, role playing games and a variety of other projects as well.

He holds a bachelor's degree in criminal justice from Indiana University, and resides in Northwest Indiana. Geologic Formation Sapphires, like any naturally occurring gemstone, are formed by the different shifts, mixings and chemical changes that are constantly taking place in the earth.

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