Tuesday, December 30, 2008

RUBY & SAPPHIRE

Ruby & Sapphire are beautiful stones. In 1995, I discovered my first ruby-sapphire-corundum deposit mixed with iolite & kyanite at Palmer Canyon west of Wheatland. After I recognized this association of gems with a rock type known as vermiculite, I started searching other vermiculites. It turns out that vermiculite is a alteration product known as glimmerite formed by retaining aluminum in the original rock & removing all silica (under pressure). Thus, one ends up with a rock that is essentially nothing but aluminum-rich mica. Ruby and sapphire are aluminum oxides are require high pressures and temperatures to form (as well as a good source of silicate poor aluminum). (photos above show one of the largest rubies found on earth at the Red Dwarf deposit. Sample is partially replaced by green zoisite; and a pink sapphire with excellent cleavage from vermiculite. Middle photo is a 1.1 carat ruby cut from material at Palmer Canyon and lower photo is a ruby from the Red Dwarf).

Earlier work in the Elmers Rock greenstone belt had shown rocks in the central Laramie Mountains formed at great pressures & temperatures that were high enough one might expect to find ruby & sapphire. So I was not surprised when I found these gems. Luckily, two geologi
sts had put together a report on vermiculite in the 1940s, so I took their publication & began searching all vermiculite deposits for ruby - about 30% contained ruby! In addition to these, other rubies were found in the southern Wind River Mountains & the source remains to be found, even though some rubies found by prospectors weighted as much as 80 carats. At another deposit in the Granite Mountains, I mapped 3000 ft of ruby schist at what is known as the Red Dwarf deposit & recovered some of the largest rubies ever found.

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