Iolite - Extraordinary Gemstone

Iolite (gem-quality cordierite) can produced some beautiful gemstones with an appearance of sapphire - but with extraordinary pleochroism! In 1996, the first, known gem-quality iolite deposit was discovered at Palmer Canyon in the central Laramie Mountains of Wyoming (Hausel, 1998). Following this discovery, thousands of carats of iolite were recovered with minor pink sapphire and ruby and considerable gem-quality kyanite. In addition, the largest known iolite gemstone in the world (in 1996) was recovered and named the 'Palmer Canyon Blue Star' - a rough gem of 1,750 carats. Several stones of more than 100 carats were also recovered.

Following this discovery, geological models were developed 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 (also known as glimmerite).

Using these 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, it was verified that Palmer Canyon contained a similar suite of gemstones including the largest iolite gemstones ever discovered (Hausel, 2004). The largest gemstone recovered was the 'Grizzly Creek Blue Giant' that weighed more than 24,000 carats. However, many gemstones of greater size were left in the outcrop. This gem was donated to the Wyoming Geological Survey and was on display at the agency on the University of Wyoming campus. If one were to assume that iolite gemstones would sell for $20 to $50/carat, this one stone alone would be worth a $ half-million to $1.2 million. With some gemstones remaining in the outcrop thought to weigh a few hundred thousand carats, the value of this gemstone deposit could be considerable.

This was followed by discovery of another giant iolite deposit known as the Raggedtop Mountain deposit further to the south in 2005 (Hausel, 2005) and this was followed by still another deposit in Helleck Canyon a short time later (Hausel, 2007).

The 1,750 carat Palmer Canyon Blue Star gemstone discovered in 1996 along with many other gemstones.

• 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.