Rhodochrosite is a manganese mineral related to the ubiquitous mineral calcium carbonate, or, calcite (common limestone is made up primarily of calcite). The calcite group of minerals includes pure calcite, dolomite, magnesite, siderite, and smithsonite, and several others. They are all carbonates with metal ions of calcium, magnesium, iron, or zinc. Calcite is noted for its many different crystal forms. Most commonly, rhodochrosite forms simple rhombohedrons and occasionally dog-tooth crystals, or scalenohedrons. Since this is a family of minerals, elements can intermix to a large degree, and form intermediate minerals. Thus, we have such things as manganocalcite, half-way between pure calcite and pure rhodochrosite. Some of the metal ions in the carbonate are calcium, some are manganese. There are other half-way minerals in this group, such as manganosiderite or cobaltocalcite.
All of these minerals are soft, usually about 3 in hardness, with three strong parting planes or cleavages. This makes cutting gemstones from them a challenge, and setting and protecting them in jewelry mountings even more of a challenge. Some of them are opaque, some translucent, and some crystal clear. The transparent ones exhibit a very strong double-refraction, as well as a high refractive index. The gemstones can be exceedingly beautiful, even though they are often so fragile as to barely qualify for the status of gemstone.
Rhodochrosite and smithsonite are often the most beautiful minerals in the group. And in fact, many collectors feel rhodochrosites can be one of the most, if not the most, beautiful crystals in the whole world. The color of pure gem rhodochrosite can best be described as a slightly orange pink-red, very close to the color of the meat of a ripe watermelon. There are occasions when rhodochrosite forms in rather homely shades of gray or brownish tones, but fortunately these are rather rare exceptions.
World-wide localities of significance include Argentina, where it forms quantities of large stalactite cave growths of bright pink banded material. This material is perfect for carving ornamental objects of great attractiveness. This type of occurrence is actually very rare, occurring here in much the same way ordinary calcite cave onyx is formed in many other places in the world. Other localities of significance include Greece, Mexico, Peru, and South Africa, as well as the United States. Pasto Bueno, Peru produced very fine gem rhombohedrons of rhodochrosite, as well as excellent specimens of quartz, huebnerite, and pyrite, among other things. The Hotazel or N'chwanning location in South Africa was remarkable for its superb clusters of water-clear dogtooth crystals. These crystals tended to have more orange tone than crystals from most other locales. The state of Montana has produced a large amount from the Emma Mine at Butte. Small amounts have been produced from scattered other states as well. Far and away the largest producer however, has been Colorado. For some geologic reason, the whole mineral belt of Colorado has many significant producers. I will only mention the most important occurrences. Starting in the east, rhodochrosite has been found south of Central City. Some fine rhombs have been found in the Moose Mine up to a couple inches across, and with some degree of transparency. The matrix is somewhat limonitic here. This mine was last worked for specimens by a group who leased the mine for such a venture in the late 1970's. It included Keith Williams and Norm and Roger Bennett. The Henderson and now defunct Urad Mines near Berthoud Pass have produced rhodo, the latter one gem rhombs with highly rounded corners and edges.
South and west in the Mosquito Range is a whole slew of mines, many of which contained at least some rhodo crystals. These include the Russia (or Little Russia) Mine, the Tanner Boy, and the most famous of all rhodochrosite mines, The Sweethome. Many fine quartz crystals, pyrites, huebnerites, fluorites, and other associated minerals have been collected from these mines as well.
The Sweethome Mine is at timberline on the Mt. Bross side of Buckskin Gulch, on the road up to Kite Lake from the town of Alma. The gulch contains some of the most interesting and spectacular mining scenery in the whole state. How the early miners got the mine buildings built on the sheer sides of the cliffs above timberline is a testimony to their sheer will and determination. The Sweethome started in the 1800's as a silver mine. Being manganese ore, the rhodochrosite crystals fouled up the silver processing and miners were encouraged to throw out as much of the rhodo as possible on the dump to avoid paying penalties at the mill. This of course, made for good collecting on the dumps years later. I started collecting there in 1976, and I did so frequently for 20 years. One Denver collector and his wife had an inside edge and found out about where an old timer had dumped a pocket of crystals in the dump. They came back with a heaping dinner plate full of crystals up to several inches long in one weekend! Collecting there was tough, as many crystals cleaved by the rough handling and broke down by weathering and turned brown to black. Many of the host rocks were stained dark red by oxidation, so you had to recognize pieces by reflections off the cleavages rather than by color alone. Some would clean up quite well with careful work in muriatic or oxalic acid. Sometimes white clay had filled the little crystal vugs and remarkably preserved the delicate crystals of quartz, fluorite, pyrite, rhodo, huebnerite, and apatite. And some would just fall apart. Your clothes always had that sulfide smell and yellow dirt stain afterward. But it was a labor of love.
In the early 90's collector/dealer Bryan Lees was able to negotiate a lease on the mine and clear enough of the government red tape hurdles to pursue his aim of operating the mine solely for the purpose of producing fine specimens. The mine had long been known for producing arguably the finest rhodochrosite specimens in the world. What followed is much expense and frustration for Bryan, but ultimately the finest assemblage of rhodochrosite crystal specimens in the world (not to mention the pyrites, needle quartzes; blue, purple and green fluorites, and other collectibles). Many of these crystals are still available to collectors. It's amazing how similar the minerals are when compared to Pasto Bueno. Both mines are right at timberline, but are a continent away. Pasto Bueno has long since mined through the good collectable crystal zone (oxidized zone). The Sweethome Mine was "permanently" shut down in 2004, but Bryan has now opened another old access (the Detroit portal), and last I heard they were able to finally get into a few gem pockets (2020).
The old Climax Molybdenum Mine near Leadville produced some magnificent crystals over the years. Unfortunately, the Amax Mining Co. took a dim view on collecting and actively worked to prevent it. Despite their efforts a few superb specimens have survived with crystals up to four or more inches long and very gemmy. Associated minerals from the veins included pyrites and fluorites. Within a few hundred yards of the southwest edge of the mine was small privately-owned tunnel called the John Reed Mine. Many gem rhombs and cleavages up to one and a half inches or more (most were more like half an inch or less) were collected here by myself and others on the dumps, until the mine was acquired by Amax and bulldozed over. Pyrite was common from here as well. Many of these crystals appeared slightly darker and oranger in color than other gem crystals from the state.
Further south in Leadville, pale pink but attractive bladed opaque crystals occurred at the Julia Fisk Mine. Similar ones were associated with galena at the Gilman Mine (famous for pyrites) to the north. West of Buena Vista near the ghost town of St. Elmo, is the Mary Murphy Mine. Small gemmy crystals have been collected there. It should emphasized that this is private property (as most all of these are) and as of the 1970's when I visited the spot, very little was left on the dumps which would tend to invite further prospecting.
Still further south over Poncha Pass is the Bonanza mining district. Attractive crystals with green fluorite were often collected at several of the mines. A few were gem quality. Most were opaque to translucent and resembled much of the material from the San Juan localities.
Westward the gorgeous San Juan Mt. mining district produced large amounts of fine specimens of rhodochrosite (as well as excellent pink or salmon manganocalcites) during the gold mining years. The last of the significant mining occurred here in the mid nineteen-eighties. The rhodo was often associated with green fluorites and fine quartz crystals. In fact, the mines of the area were famous for not only gold and silver, but the sulfide mineral crystals as well, such as chalcopyrite, iron pyrite, galena, sphalerite, and many others. Most of the crystals were not gemmy or large, but rather opaque or translucent pink. However, they were still very attractive as mineral specimens. The most famous mine here for rhodo was the American Tunnel in the Sunnyside vein near Silverton. At one time they seemed to come out of there in a never ending supply. Some crystals reached two or more inches and were gemmy on the inside. Most were much smaller, but some warped, saddle-shaped crystals were found, as well as a few of the bladed variety. The massive pink ornamental gemstone rhodonite (manganese silicate, sometimes now called pyrox-mangite) also came from there in large quantity. Other mines that produced rhodo in some quality or quantity include the Grizzly Bear Mine, the Mountain Monarch, and the Michael Breen Mine.
Most of these mines are on private property. Collecting may or may not be permitted on the dumps, depending on the timing of your visit. Often the surface of the dumps have been picked over pretty thoroughly, and you will have to rake and turn over pieces on the dump or dig to find things. Old mines can be very hazardous. The mines themselves can cave in easily, have bad air or gas pockets or have hidden shafts that can be easily fallen into. One such collector fell to his death in an old gold mine on Mt. Bross not too many years ago while looking for rhodochrosite crystals. Never go into an old mine without permission and a trained geologist and proper equipment along (hardhats, lamps, etc.), and then be extremely cautious. Sulfide deposits can represent environmental hazards as well, and gold mines often use cyanide leaching ponds. Even the dumps and old fallen mine buildings can present definite dangers. Most of these sites are no place for young kids. Please use common sense and be respectful of mining claims and property, as it only takes one negative incident to close an area completely to collecting.
***End of My Rhodochrosite Blog. If you have any questions or comments on this article, you are welcome to email me. ***