Sunday, December 9, 2012

Iolite - Extraordinary Gemstone

Beautiful gem-quality iolite in outcrop at Grizzly Creek.
Note the yellow-brown limonite adjacent to the blue iolite. This is mineral
 rust: the iron-rich iolite has a rusty surface and everything sitting under
this rust is also gem-quality iolite. Note the scale on the rock, this
scale is in inches.
Iolite (gem-quality cordierite) can produce beautiful gemstones with an appearance of sapphire - but with the addition of extraordinary pleochroism (this means simply that it tends to change color as the gem is rotated in light)! In 1996, the first, known gem-quality iolite deposit was discovered at Palmer Canyon in the central Laramie Mountains of Wyoming (Hausel, 1998). At the time, iolite was one of the rarest gemstones on earth. Following discovery, thousands of carats of iolite were recovered with minor pink sapphire, some ruby and considerable gem-quality kyanite. The largest known iolite gemstone in the world in 1996 was also found by the author and named the 'Palmer Canyon Blue Star' - a rough gem of 1,750 carats. Several stones of more than 100 carats were also recovered at the time.

Following discovery, geological models were developed by the author to assist in a search for similar gemstone deposits (Hausel, 2002, 2007; Hausel and Sutherland, 2000, 2006). In particular, these types of deposits (iolite and kyanite) were typically found in alumina-rich metamorphic rocks of moderate amphibolite grade. Whereas the nearby rubies and sapphires were located in a silica-poor vermiculite schist (known as glimmerite).

Using geological models, it was predicted in 2000 that Grizzly Creek south of Palmer Canyon would likely be a similar deposit as Palmer Canyon (Hausel and Sutherland, 2000). Thus in 2004, we verified my geological model and proved that Palmer Canyon contained a similar suite of gemstones including the largest iolite gemstones ever discovered (Hausel, 2004). The largest gemstone I carried out, I named the 'Grizzly Creek Blue Giant' which weighed more than 24,000 carats! But this detrital stone was dwarfed by the giant stones we left in the outcrop since we lacked the proper tools to carve them out of the hard rock.

Selection of faceted iolite and ruby gemstones from Palmer Canyon.
The Grizzly Creek Blue Giant gemstone was donated to the Wyoming Geological Survey and was put on display on the first floor of the agency at the University of Wyoming campus. If one were to assume iolite gemstones would sell for $20 to $50/carat, this one stone alone could produce $500,000 to $1.2 million in faceted gems. With some gemstones remaining in the outcrop that likely weigh hundreds of thousands of carats, the value of this gemstone deposit could be considerable.

But the discovery was followed by discovery of another giant gemstone iolite deposit by myself known as the Ragged top-Sherman Mountain deposit further to the south in 2005 (Hausel, 2005) and this was again followed by another deposit in Helleck Canyon a short time later (Hausel, 2007).

  • Hausel, W.D., 1998, Field Reconnaissance of the Palmer Canyon corundum-kyanite-cordierite deposit, Laramie Mountains Wyoming: Wyoming State Geological Survey (WSGS) Mineral Report MR98-1, 7 p.
  • Hausel, W.D. 2002, Gemstones, Semi-Precious Stones, Lapidary Materials, Ornamental Stones and Other Unique Minerals and Rocks in Wyoming, Rocky Mountain Section, Geological Society of America 54th Annual Meeting, abstract no. 33540, p. A54.
  • Hausel, W.D., 2004, Geological Reconnaissance of the Grizzly Creek Gemstone deposit – Potential Source for Iolite, Sapphire, Ruby & Kyanite WSGS Open File Report 04-14, 8 p.
  • Hausel, W.D., 2005, Geologists Locate Giant Gemstones: Prospecting and Mining Journal, v. 74, no. 7, p. 7-9.
  • Hausel, W.D., 2007, Gemstones of Wyoming - Recent discoveries: Colorado Geological Survey Industrial Minerals Forum, 12 p. 
  • Hausel, W.D., and Sutherland, W.M., 2000, Gemstones & Other Unique Minerals & Rocks of Wyoming - A Field Guide for Collectors: Wyoming Geological Survey Bulletin 71, 268 p. 
  • Hausel, W.D., and Sutherland, W.M., 2006, World Gemstones: Geology, Mineralogy, Gemology & Exploration: WSGS Mineral Report MR06-1, 363 p.

8 comments:

  1. This comment has been removed by the author.

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  2. Dan, You are amazing, and so are your discoveries!

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