- Thumbnail, 1.8 x 0.7 x 0.5 cm
- N'Chwaning Mines, Kuruman, Kalahari manganese fields, Northern Cape Province, South Africa
Gaudefroyite is a very rare calcium, manganese borate found at only four localities worldwide, three of which, are in the Kalahari Manganese Field of South Africa. This is an exceptionally rare and large, doubly-terminated, jet-black crystal with high luster. The terminations are sharp and the crystal is complete-all-around.