Ruby is corundum colored by a trace of chromium. In sapphire, manganese produces pink shades, and the blue color is caused by a combination of iron and titanium. Iron alone results in shades of yellow and green. Many sapphires contain excess titanium, which appears in the form of included tiny needles of titanium oxide (rutile) and is called "silk". (rutile in larger crystals also occurs in quartz, where it creates amazing bursts and sprays of golden needles).
The silk in a sapphire can be removed, and the stone made visually cleaner, by heating (at high temperature the rutile dissolves into the corundum structure). Montana sapphires have been known for more than a century, and in fact were once intensively marketed by tiffany and co. Sapphires in montana occur in many distinct colors, but are usually zoned, with several colors present at the same time. Careful heating removes the silk, but also intensifies the colors and helps to create many distinctive hues, depending on the chemistry of the original crystal. The visual appearance of several colors is a distinctive characteristic of rock creek and missouri river, montana sapphires.
Yogo material is unique in that has lovely blue coloration when mined and does not require any form of treatment whatever. Unfortunately, yogo crystals are shaped like thin wafers and are seldom transparent, so clean gems over melee size are extremely rare, and stones over 1 carat are collector items. Most people do not know that yogo sapphires do occur in many colors, but the vast majority are blue or violetish in hue. The "precious" stones are generally said to be diamond, ruby, sapphire, and emerald (opal and pearl are sometimes included). The value of these gems is a function of size, color and clarity, with "pure" colors being the most desirable.A kashmir sapphire is a true rarity, and extraordinarily expensive, because of its intense pure dark blue color, with only a tinge of violet. This amazing natural, untreated blue montana sapphire is atypical for the locality, not only being near top quality, displaying a fine medium-dark slightly violetish blue color, but is exceptional in terms of size and clarity. Sapphire is the birthstone for september. Surveys of the jewelry industry have been done yearly to assess gemstone popularity, and for the past five years blue sapphire has been consistently number one on the list. The price is for the one blue sapphire, that we guarantee to be from yogo gulch in montana and no treatment has been applied.
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