N'Chwaning II ettringite is one of the great paradoxes of modern mineral collecting: a soft, water-rich cement-mineral species that, at this locality, became a cabinet-level showpiece. The best examples are lemon- to sulfur-yellow, glassy to silky, and sharply hexagonal, often with the kind of saturated yellow that collectors more readily associate with sulfur than with a calcium aluminum sulfate hydrate. On fine crystals the color is not a surface stain but an internal glow, especially in translucent prisms where the broad hexagonal faces show growth zoning, fine striations, and a waxy-gemmy brightness.
Photo: Wikimedia Commons / Rob Lavinsky, iRocks.com
The mineralogical setting is the northern Kalahari Manganese Field, one of the world’s most important manganese deposits and a locality suite famous for rare, unusual, and beautiful species. N'Chwaning II is part of the Black Rock–N'Chwaning–Gloria mining complex in the Northern Cape, where high-grade manganese ore occurs in the Hotazel Formation of the Transvaal Supergroup. Later hydrothermal alteration, faulting, and upgrading of the manganese ore created the open spaces and chemical environments that gave collectors species such as rhodochrosite, hausmannite, manganite, inesite, olmiite, gaudefroyite, sturmanite, jouravskite, charlesite, and ettringite.
Photo: Wikimedia Commons / Rob Lavinsky, iRocks.com
For collectors, the appeal is highly visual but the discipline is analytical. Ettringite, sturmanite, jouravskite, and charlesite are closely related members of the ettringite group, and N'Chwaning material can be visually treacherous. Yellow hexagonal prisms from the mine may be sold under one of these names based on old labels or appearance, but visual identification alone is not reliable. That caveat has become part of the locality’s collecting culture: a top N'Chwaning II “ettringite” is prized for color, form, and provenance, but the best-documented examples carry analytical confidence or come from collections and dealers with careful species work.
The historical importance is also real. N'Chwaning II came into production in 1981, and the majority of the celebrated N'Chwaning mineral finds documented by collectors have been associated with this shaft. Ettringite from the mine was sufficiently notable to receive a dedicated “Connoisseur’s Choice” article in Rocks & Minerals in 2012. That placement matters: it marked N'Chwaning II material not merely as a colorful curiosity, but as one of the species’ defining collector occurrences.
Search for specimens: View all ettringite specimens from N'Chwaning II Mine, South Africa
N'Chwaning II Mine is one of the N'Chwaning manganese mines in the Joe Morolong Local Municipality, John Taolo Gaetsewe District Municipality, Northern Cape, South Africa. The locality lies in the Kalahari Manganese Field near Kuruman and Hotazel, within the broader Black Rock mining area. The N'Chwaning mines take their name from the farm N'Chwaning 267.
The deposit is a stratabound manganese ore system hosted by the Hotazel Formation of the Griqualand West Sequence, part of the Proterozoic Transvaal Supergroup. The Kalahari Manganese Field is a Paleoproterozoic chemical-sedimentary system in which manganese-rich layers are intercalated with banded iron formations and carbonates. In the N'Chwaning–Wessels–Black Rock sector, the ore was later modified by fault-controlled hydrothermal alteration, producing coarser, higher-grade Wessels-type ore and an extraordinary suite of collector minerals.
The mine is an underground manganese operation, worked by mechanized bord-and-pillar methods. Assmang lists Nchwaning 2 as commissioned in 1981, producing high-grade oxide ore with Nchwaning 3. Mindat records the N'Chwaning II shaft as a 450 m shaft with an underground crushing station that came into production in 1981; Assmang’s current operations page gives the Nchwaning 2 shaft depth as 421 m. The difference reflects how shaft depths and mine descriptions are reported in different operational and locality references, but both sources agree on the 1981 production start.
The mining history of the complex begins with Assmang’s acquisition in 1940 of a manganese ore outcrop at Black Rock. The mining district developed through the Gloria and N'Chwaning operations, and N'Chwaning II became the shaft most strongly associated with major collector finds. N'Chwaning III later expanded the operation, while N'Chwaning II continued to be important both as mining infrastructure and as a source of specimens.
Collecting access is not comparable to a surface rockhounding locality. N'Chwaning II is an active underground mine in a commercial manganese operation. Specimens have entered the collector market through mine-related recovery, miners, local handlers, and dealers, not through casual public collecting. The very conditions that make the specimens possible—freshly opened ore faces, pockets in hard manganese ore, underground heat, humidity, blasting, and strict safety procedures—also make independent access unrealistic.
Notable N'Chwaning II mineral finds are not confined to ettringite. The shaft is central to the reputation of the whole N'Chwaning suite, including rhodochrosite, manganite, hausmannite, olmiite, gaudefroyite, and other manganese-field specialties. Ettringite stands out because it is delicate, highly hydrated, and chemically close to several look-alike species, yet from this mine it occurs as sharp, aesthetic crystals large enough for serious display specimens.
Ettringite has the ideal formula Ca6Al2(SO4)3(OH)12·26H2O. It is very soft, with a Mohs hardness of about 2 to 2.5, perfect cleavage on 1010, and a low density around 1.77 g/cm3. Those physical properties matter greatly for N'Chwaning II specimens: even the most imposing crystals are mechanically vulnerable, and a large crystal that is truly sharp, lustrous, unrepaired, and undamaged is far rarer than its simple chemical formula might suggest.
The classic N'Chwaning II form is a hexagonal prism, commonly thick, sometimes barrel-like, with flat to pyramidal terminations. Fine crystals may be translucent to gemmy, with internal yellow color ranging from pale straw and powder-lemon to strong sulfur-yellow. Some crystals show faint longitudinal striations, stepped growth, or slight zoning. The best single crystals have a crisp hexagonal outline, glassy luster on terminal faces, and enough transparency to glow when backlit.
Verified photographed examples from N'Chwaning II show several collector modes. One 8.2 x 6.2 x 3.4 cm plate is made of many small gemmy lemon-yellow hexagonal crystals up to about 0.5 cm, creating a sugary druse. Other miniatures are dominated by a single sharp crystal around 3 cm tall. A photographed 3.2 x 1.7 x 1.4 cm example is a lustrous sulfur-yellow prism with textbook form and a smaller “sidecar” crystal near the termination. Another 3.4 x 2.4 x 1.1 cm example is a doubly terminated lemon-yellow floater attributed to early-1980s finds. Contemporary market records also document exceptional groups with crystals to about 5 cm, which are large for the species and especially desirable when the color remains clean and the crystals are not chalky from dehydration.
Associated minerals are part of the aesthetic language of the locality. Ettringite may occur with calcite, manganite, gaudefroyite, and manganese-ore matrix, and broader N'Chwaning II assemblages include hausmannite, hematite, braunite, andradite, rhodochrosite, olmiite, oyelite, and other calcium-manganese silicates and carbonates. Black gaudefroyite beside pale yellow ettringite is a particularly attractive contrast; dark manganese oxides or manganite can make the yellow stand out dramatically.
Quality is judged by a small set of unforgiving factors. Color comes first: strong lemon-yellow is preferred over washed-out straw, grayish yellow, or brownish yellow. Transparency and luster follow closely. Sharp terminations are crucial because many crystals are contacted, bruised, cleaved, or edge-chipped. Matrix can add value when it creates contrast or balance, but a single freestanding or doubly terminated crystal can be more desirable than a larger but jumbled group. Provenance is unusually important because of the species-identification problem; an old label from a respected collection is useful, but analysis is better.
The central authenticity issue is not a wave of documented fakes or common treatments; it is correct naming. Ettringite, sturmanite, jouravskite, and charlesite from N'Chwaning cannot be reliably separated by eye. Mindat’s locality note is unusually blunt on this point: visual properties and mineral associations are not enough. Serious collectors should treat old “ettringite” labels with respect but not with blind confidence, especially for high-value pieces. For important specimens, Raman spectroscopy, X-ray diffraction, electron microprobe work, or other analytical confirmation is the proper standard.
This problem cuts both ways. Some pieces sold as ettringite may be sturmanite, jouravskite, charlesite, or zoned/intergrown material. Conversely, genuinely analyzed ettringite can be undervalued when it sits among visually similar yellow ettringite-group minerals. Provenance to an old collection, a reputable dealer, or a published specimen helps, but analytical documentation is the best premium.
Condition is the other major concern. Ettringite is soft, hydrated, and cleavage-prone. Broken terminations, bruised prism edges, contacted back faces, and cleaved bases are common. Partial dehydration can make ettringite turn paler or whitish, so avoid prolonged heat, strong direct sunlight, very dry storage, and aggressive cleaning. Ultrasonic cleaning is inappropriate. Even water cleaning should be approached cautiously; dust removal with a soft brush and stable display conditions are safer.
Specimens should be mounted securely and handled as little as possible. A crystal that looks chunky may still separate along cleavage or crumble at damaged edges. If a specimen is boxed, the mount should immobilize the piece without pressing against terminations. For display, vibration and accidental contact are bigger risks than light alone, though avoiding hot lamps is wise.
Rarity depends strongly on quality tier. Small yellow clusters and modest thumbnails appear on the market from time to time. Sharp, lustrous, analytically credible N'Chwaning II crystals over 2 cm are much scarcer. Fine miniatures with complete terminations are desirable, and cabinet groups with crystals in the 4–5 cm range are exceptional. Large, clean, undamaged specimens with strong color and old provenance can command serious prices.
The most vivid account of N'Chwaning II collecting is not a tale of ettringite alone, but of the underground world that produced the specimens. In 2017, Cape Minerals published a field note recalling a descent made years earlier into the N'Chwaning II shaft. The visit began at the headgear, seen in 2007 on the way to the mine portal, and then moved into the practical discomfort of an underground mine: a hardhat lamp heavy on the head, loose overalls holding heat, and hands gripping the bar of the mine vehicle as it rolled toward the portal.
Before entry, the vehicle passed a braking test on a large steep bump, a simple but sobering reminder that underground collecting begins with mine safety, not with minerals. The writer remembered the thought that came at that moment: “Down the rabbit hole we go.” Below ground, N'Chwaning II became less a tunnel than an underground city, with engineering stations, safe rooms, vehicle bays, maintenance areas, rest areas, and sidings where large equipment could pass on underground roads.
The sensory details explain why specimen extraction at N'Chwaning II has never been a casual collector’s pastime. The account describes 100 percent humidity, the smell of a recent blast, and rock dust coating the tongue. At the working face, the team stopped only after another inspection for rock stability and safety. Then the collector’s instinct took over: small cavities appeared in the hard manganese ore, their contents muted by underground lighting, and the tools came out.
The work was slow and physical. Some pockets extended deep into the sheer face, requiring heavy equipment and hours of labor. The heat was not abstract; the rock itself felt warm, and high humidity made cooling down almost impossible. Specimens were packed in old cloth inside plastic containers before being taken to the surface. On that trip the majority were manganocalcite pieces, many with sprays and tufts of kutnohorite rather than ettringite, but the scene applies directly to the mine’s specimen culture: careful underground recovery, rough conditions, and a moment of revelation only after the pieces reached daylight.
That daylight moment is the emotional center of the story. Underground lighting had washed out the minerals. In the sun, some of the specimens were seeing daylight for the first time, and their color and sparkle emerged all at once. It is easy to understand why old N'Chwaning labels can be so specific about shaft, year, and pocket. In a locality where specimens come out through sweat, permission, and dangerous work, the memory of a find is not just paperwork; it is part of the specimen.
Amethyst
Quartz
Fluorite
Tourmaline
Malachite
Azurite
Rhodochrosite
