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Rhyolite From Topaz Mountain, UT

View From Topaz Mountain, Juab County, Utah. Photo by Phil Konstantin

View From Topaz Mountain, Juab County, Utah. Photo by Phil Konstantin

A few weeks ago the USU Mineralogy class took an overnight field trip to Topaz Mountain in Juab County, Utah. This location is known for an abundance of semi-precious gemstone, namely a champagne colored topaz, opal, and red beryl. Unfortunately, the topaz loses its color after exposure to UV radiation (sunlight) so the gemstones, although beautiful, aren’t super valuable.

Of more interest to me, of course, was the rhyolite material itself. After working quite a bit with the ultramafic (high in magnesium and iron) basalts from the Snake River Plain in Idaho, I was coming to the conclusion that I needed to add in silica and alumina to stabilize this glaze and keep it from flowing off of my pots as well as having a nice and glossy glaze surface. Quite by luck, I was in the perfect spot to find a material that was precisely what I needed to mix together with my basalt material to get something interesting.

In the end, I had a lot of fun busting open rocks and attacking the rhyolite outcrops with a 5 pound sledge. I took some pictures of some of the coolest, and largest topaz pockets, which are referred to as “vugs”. At the end of the day I filled up a 5 gallon bucket with this material and brought it back to the studio to go straight into the ball mill. More on the results in a later post!

 

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A vug I unearthed filled with Amber Topaz.

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More vugs filled with the distinct champagne colored Topaz. Unfortunately these topaz lose color with exposure to sunlight.

 

From the paper 'Geochemical evolution of topaz rhyolites from the Thomas Range and Spor Mountain, Utah. - Christiansen, Bikun, Sheridan, Burt, 1984

From the paper ‘Geochemical evolution of topaz rhyolites from the Thomas Range and Spor Mountain, Utah. – Christiansen, Bikun, Sheridan, Burt, 1984

 

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