Introduction

N’Chwaning rhodochrosites have stunned the mineral world with their deep red color and superb clarity. The N’Chwaning Mines have produced some of the gemmiest and most lustrous rhodochrosite crystals known, rivaling the best of the Sweet Home Mine. What makes N’Chwaning rhodochrosite unique is the great variety of crystal habits and hues. The most magnificent specimens to come out were large, blood-red scalenohedral crystals.

The N’Chwaning Mines actually consist of N’Chwaning I, and N’Chwaning II and III Mines, which are shafts leading from N’Chwaning I. Before diving deeper into the N’Chwaning Mines, here is a brief look at the general history of the Kalahari Manganese Field. The N’Chwaning Mines are situated in the Kalahari Manganese Field, which is the world’s largest and richest manganese deposit.

Located within the KMF is the Hotazel Formation, a geologic formation known for its manganese-rich sedimentary rocks and banded iron formations. Within the Hotazel Formation there are about 22 mines, most of them inactive now. Of these mines, the key rhodochrosite-producing mines are the Hotazel Mine, Wessels Mine, and N’Chwaning I, II, and III Mines.

In 1926, Guido Sacco, a young Italian mining engineer and geologist, came to South Africa, where he played a crucial role in the development of the Kalahari Manganese Field. Guido recognized the potential of this region and formed Gloucester Manganese Mines Ltd. (which he later merged to create ASSMANG) to secure deposits for mining. In 1940, he obtained mineral rights to the Black Rock Mine, which began operation that same year. The Hotazel Mine opened in 1959; however, it wasn’t until 1963 that a find of rhodochrosite surfaced.

The original rhodochrosite specimens from this find were not very striking. These drusy specimens were usually associated with gypsum. In the years 1964–1967, however, the underground workings of the Hotazel Mine yielded large and spectacular scalenohedral and trigonal wheat-sheaf crystals of rhodochrosite which became world-famous.

The N’Chwaning I Mine opened in 1972 and consisted of underground workings. In 1977, a major discovery was made at the working face of the N'Chwaning I Mine, revealing a vuggy zone rich in rhodochrosite of the finest quality. Miners rushed to gather what they could, resulting in the recovery of hundreds of specimens, including many world-class pieces. Unfortunately, many specimens were lost or destroyed in the process.

This discovery produced clusters of scalenohedral crystals measuring up to 20 cm or larger, exhibiting deep red colors and mirror-like reflectivity, with individual crystals reaching 7 cm in size. This find is said to be the best to ever come out of the KMF. Both the number of specimens and the diversity of habits that came out of the N’Chwaning I were far greater than what came out of Hotazel.

The crystals of N’Chwaning I Mine exhibit a wide range of colors, from pale and rose pink, to blood red, and they can be opaque, translucent, or transparent. The habits include smooth-surfaced or drusy pink spheres, spherical groups of scalenohedral crystals, aggregates that have a mushroom-shape, and translucent pink platelets (lenticular). The most common (and exceptional) crystal habit is, of course, the scalenohedron.

These scalenohedra can occasionally be overgrown by second-generation crystals with flat pinacoid terminations and are sometimes associated with minor white calcite. Another habit seen from this mine is the distinct wheat-sheaf habit, where crystals form tiny (usually about 1 cm) bundles that are pale pink and opaque in the middle and red and transparent on the ends. This habit formed both as clusters of floater crystals as well as on matrix. These wheat-sheaf crystals are unlike the “trigonal” wheat-sheaf habit seen at the Hotazel Mine.

The Wessels Mine began operation in 1973, and sporadically produced pink rhombohedral crystals of rhodochrosite, as well as drusy botryoidal plates. The N’Chwaning II Mine opened in 1981 and yielded minor rhodochrosite occurrences. In 2006, there was a small find that produced a few dozen specimens with pink rhombohedral crystals on matrix.

The N’Chwaning III Mine became fully operational in 2005, and it is still being mined today. There was a limited find in 2015, which mostly produced opaque pale pink drusy crusts composed of tiny rhombohedral crystals of rhodochrosite.

Availability: The N’Chwaning Mines are still operational for manganese but are not currently producing rhodochrosite. Good N’Chwaning rhodochrosites are therefore rare on the market, and, when they appear, they often fetch high prices rivaling Sweet Home pieces.