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April7, 2018 Weekly Geology Guest, Olivine

April 8, 2018
Greetings from the Bluff Park Back Porch, way up yonder on Shades Mountain (1,109′) in Alabama:
This week’s industrial mineral is Olivine.

 

What is Olivine?

Olivine is the name of a group of rock-forming minerals that are typically found in mafic and ultramafic igneous rocks such as basalt, gabbro, dunite, diabase, and peridotite. They are usually green in color and have compositions that typically range between Mg2SiO4 and Fe2SiO4. Many people are familiar with olivine because it is the mineral of a very popular green gemstone known as peridot.

The mineral olivine ( /ˈɒlɪˌvn/) is a magnesium iron silicate with the formula (Mg2+, Fe2+)2SiO4.

Olivine Locality: Naran-Kagan Valley, Kohistan District, North-West Frontier Province, Pakistan (Locality at mindat.org) Size: miniature, 3.4 x 2.5 x 1.9 cm (28 grams) Peridot This is from a new find of peridots at this now-classic locality which has produced the world’s best crystals of the species by far. The color is just a REALLY JUICY LIMEY-GREEN COLOR the likes of which you seldom see. The crystal is very gemmy and translucent to transparent throughout, as well, so it is better in person than the photos indicate. I know these have been comin gout for years now, but THIS type is different – just a bit more vibrant in color, overall, and with great terminations. This was one of the few miniatures I picked up for a mix of form and color quality. There are a few very insignificant dings, and one contact on the left side. It is otherwise complete all around.

Olivine-gem7-10a.jpg
Rob Lavinsky, iRocks.com – CC-BY-SA-3.0
 

Translucent olivine is sometimes used as a gemstone called peridot (péridot, the French word for olivine). It is also called chrysolite (or chrysolithe, from the Greek words for gold and stone). Some of the finest gem-quality olivine has been obtained from a body of mantle rocks on Zabargad Island in the Red Sea.

Olivine gemstone

Olivine gemstone: The gemstone known as peridot is a variety of olivine. These two faceted stones are nice specimens of yellowish green peridot. The gem on the left is a 1.83 carat cushion cut peridot of about 8 x 6 millimeters from Myanmar. The gem on the right is a 1.96 carat cushion checkerboard cut peridot of about 10 x 8 millimeters from China. Photo copyright Geology.com.

Olivine in pallasite

Olivine in pallasite: A part slice of the Esquel pallasite from Chubut, Argentina. The large, colorful, oblong olivine crystals are typical of this meteorite. Note the way in which crystals near the rough (natural) edge have turned orange and yellow due to terrestrial weathering, while the crystals nearer to the center of the original mass have retained their true olive green color. Photograph by Geoffrey Notkin, copyright Aerolite Meteorites, used with permission.

 

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>    Since olivine makes up the mantle, it is used to determine depth of burial, thus temperature and pressure.
Olivine grains which eroded from lava on Papakolea Beach, Hawaii

 

Wilson44691Own work
 
Uses:

Olivine is a used as a substitute for dolomite in steel works.[34] Olivine is also used to tap blast furnaces in the steel industry, acting as a plug, removed in each steel run.[citation needed]
The aluminium foundry industry uses olivine sand to cast objects in aluminium. Olivine sand requires less water than silica sands while still holding the mold together during handling and pouring of the metal. Less water means less gas (steam) to vent from the mold as metal is poured into the mold.[35]
In Finland, olivine is marketed as an ideal rock for sauna stoves because of its comparatively high density and resistance to weathering under repeated heating and cooling.
 
{Sounds like a nice christmas present!} R
 
 
We will now continue down the Industrial Mineral dusty trail and continue with https://en.wikipedia.org/wiki/Zeolites.
 
Enjoy the adventure!
 
Thanks,
 
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