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Durability of Fire Opal
Fire opal has a Mohs hardness of 5.5 to 6, which is soft enough that it can be scratched by many objects that it might encounter during everyday wear. Fire opal also has a low tenacity, which means that it can easily be chipped or broken. Fire opal is best used in jewelry such as earrings, pins,…
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Fire Opal Value
The value of a fire opal is based upon the desirability and uniformity of its color, with yellow being on the low end of value and red being on the high end. Transparent stones are preferred over translucent stones. The best fire opal typically sells for prices that are much lower than the best precious…
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How are Fire Opals Cut?
Fire opals are cut in a variety of ways. Some are cut as faceted stones, others are cut as cabochons. The cutter decides how he/she thinks the stone will be most attractive. There is no rule for cutting fire opal. Transparent fire opals are most often faceted so that they can be illuminated by incident…
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Precious Fire Opal
A few specimens of fire opal exhibit “play-of-color”. These specimens have both the fiery background color of a fire opal and the play-of-color of a precious opal. Some people call these special stones “precious fire opal”. The play-of-color can be tiny bright flashes of color when the opal is played under light, or a billowing…
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What is Fire Opal?
Many people confuse “fire opal” with “precious opal”. So, here is a quick lesson on the three basic types of opal. The name “fire opal” is all about the bodycolor – fiery yellow, fiery orange or fiery red. It’s not about “flash”.
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Olivine and the Gemstone Peridot
Olivine is also the mineral of the gemstone known as “peridot.” It is a yellow-green to green gemstone that is very popular in jewelry. Peridot serves as a birthstone for the month of August. The most valued colors are dark olive green and a bright lime green. These specimens are of the mineral forsterite because the iron-rich fayalite is…
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Uses of Olivine
Olivine is a mineral that is not often used in industry. Most olivine is used in metallurgical processes as a slag conditioner. High-magnesium olivine (forsterite) is added to blast furnaces to remove impurities from steel and to form a slag. Olivine has also been used as a refractory material. It is used to make refractory…
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Olivine Rain on a Developing Star
In 2011, NASA’s Spitzer Space Telescope observed what is believed to have been tiny crystals of olivine falling like rain through the dusty cloud of gas of a developing star. This “olivine rain” was thought to have occurred as strong air currents lifted newly crystallized particles of olivine from the surface of the forming star,…
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Extraterrestrial Olivine
Olivine has been identified in a large number of stony and stony-iron meteorites. These meteorites are thought to have originated from the mantle of a rocky planet that used to occupy an orbit between Mars and Jupiter – or they might be from an asteroid that was large enough to have developed a differentiated internal structure consisting of a…
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Physical Properties of Olivine
Olivine is usually green in color but can also be yellow-green, greenish yellow, or brown. It is transparent to translucent with a glassy luster and a hardness between 6.5 and 7.0. It is the only common igneous mineral with these properties. The properties of olivine are summarized in the table. Physical Properties of Olivine Chemical Classification Silicate Color Usually…