HyaliteThe glassy form of opal can display the internal play of colour that characterises precious o
HyaliteThe glassy form of opal can display the internal play of colour that characterises precious opal, but on its own it can be visually stunning like this 3cm amorphous blob on matrix from Poland. In the gem trade it is often referred to as water opal for its limpid transparency, and its usual habit is in these bubbly accretions mineralogists term renniform (kidney shaped). Unlike many gems it doesn’t crystallise from minerally charged fluids, but from the gas phases in vugs and pockets in volcanic rocks, much like the red beryls found in Utah (see http://tinyurl.com/olaegwd). It also glows brightly in Uv light.LozImage credit: Howie516http://www.mindat.org/min-1959.htmlhttp://webmineral.com/data/Opal.shtml#.VEbLmBYjwzQ -- source link
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