Sweet Home Rhodochrosite

The color of a faceted gemmy transparent rhodochrosite—a fluorescent vivid medium dark orange-, sometimes reddish, pink—is so distinctive of the species that displays at gem shows always cause a traffic jam in the aisles.

Faceted Sweet Home rhodochrosite, named for the Colorado site from which it’s mined, is a rare gem find that for the past 10 years has been downright scarce. But a bit of bad luck for the mine turns out to be good luck for gem faceters.

History. Most rhodochrosite is opaque ornamental banded bacon-strip white-and-pink material usually crafted into eggs, animal carvings, and the like. It’s been known for more than a century but has received scant attention in the jewelry industry, mainly because of its relative softness. Rhodochrosite was described by gemologist Max Bauer in his 1897 Precious Stones as “too soft to be worked even for ornamental purposes.”

The Sweet Home Mine, originally called the Home Sweet Home, was first claimed in 1873. This Colorado silver mine produced silver and mineral ore off and on for about 60 years. But from the 1930s until the early 1960s there was no notable strike of rhodochrosite or silver. In the ’60s the mine owners tried to pick up where miners left off in 1925, the year of the last big silver strike.

When that didn’t work out, the mine owners decided to look for rhodochrosite instead of silver. They searched the old records and eventually found a seven-foot long pocket filled with rhodochrosite crystals, just a few feet from the 1925 silver strike. That was the last significant find of rhodochrosite until the current mining project began in 1991.

The 1991 mining venture, led by Bryan Lees of Golden, Colo., began as a rhodochrosite mineral specimen recovery project. The Sweet Home mine, like any typical mine, uses drilling and blasting, but to find rhodochrosite, ground-penetrating radar and surface electromagnetic surveys also have been used. Once a pocket of gems is opened, medical fiber-optic scopes are used to peer into the deeper pockets, and diamond saws are often necessary to remove them from the rock. Sometimes miners find crystals that come within millimeters of touching the other side of the hard rock. If they can get them out, they have a specimen to sell.

However, if the miners accidentally blast through a pocket, or if crystals are so large that they were “ruined” by touching the other side of the pocket, the result is faceting rough. The better the miners are at taking crystals out, the harder it is to get material to facet. In fact, they’ve been so good at finding and recovering specimens that no one has had much material to facet since 1992 when they unearthed the last large find of facet-grade material.

Colors. Rhodochrosite has a narrow range of color. It’s colored by manganese, which typically results in combinations of red, pink, and orange hues. Sweet Home material is typically color-graded as more pinkish-orange to orangey-pink than red, with top quality described as medium dark to dark, vivid, pink-orange.

South Africa, Peru, Japan, and Argentina also produce transparent rhodochrosite, although Argentina is noted more for its opaque ornamental rhodochrosite than for transparent gemmy material. The African material is quite red, but supplies are even rarer than those from Sweet Home. Peruvian material can look very similar to Colorado rhodochrosite, but not much has been produced in the past 10 years. The Japanese and Argentinean material has been described as “less neon” than Sweet Home gems—more like cherry Jell-O.

Qualities. Color and transparency are the two most significant qualities for this material. Clarity is considered only if there are eye-visible and distracting inclusions. As for the importance of size, 1-ct. to 3-ct. sizes are respectable. Anything over 10 cts. is considered a significant stone.

Prices. According to Paul Cory at Iteco in Powell, Ohio, prices for fine-quality 1-ct. to 3-ct. Sweet Home faceted gems can range from $75/ct. to $100/ct., and 3-ct. to 5-ct. stones can be priced from $95/ct. to $150/ct. Larger gems (10-plus cts.) start at approximately $200/ct. Mineral specimens are priced according to quality, size, supply, and demand.

Enhancements. Transparent rhodochrosite doesn’t need enhancing.

Bench care and cleaning. Approach this one with caution. It has three perfect directions of cleavage, so one good hit means you’ll have two or three stones instead of one. So mounting in a ring is out.

That’s toughness. But what about hardness? Rhodochrosite is a soft gem, 3.5-4 on the Mohs scale, and is easily scratched. Don’t use a rouge cloth for cleaning.

And don’t use steam or ultrasonic cleaning. The biggest problem with the ultrasonic is not vibration but heat. Thermal shock on rhodochrosite is bad news. Some say it’s a result of the heat expanding the fluid inclusions, causing the cleavage planes to part.

One interesting note on this gem’s durability: Because the Sweet Home mine is so well documented, each stone has a unique registration number when sold by the mine. Experts can tell you which gem came from which pocket, and whether or not the gem is more likely to have problems due to its proximity to a blast.

Recommended reading. For more information, see “Gem Rhodochrosite from the Sweet Home Mine, Colorado,” by K. Cox and B. Lees, Gems & Gemology, Summer 1997; “Gem & Crystal Treasures,” by Peter Bancroft, The Mineralogical Record, 1984; and “Sweet Home Mine,” Mineralogical Record, July-August 1998.

Special thanks to Paul J. Cory, owner of Iteco, Inc., Powell, Ohio, (614) 923-0080;www.itecoinc.com.