Willemite, Calcite & Dioptase from Gotala, Republic of the Congo

by | Specimens

A streak of light green willemite crystal on a calcite matrix with a few, deep green, gemmy dioptase crystals as special guests. The willemite crystals are quite small, between 1 and 2 mm, but are all well formed, translucent, light green in color and there are scores of them! The nicest dioptase crystal is in the bottom left corner, perfectly formed, about 1 cm tall. More are on the back, but quite dirty. Most interesting is the fluorescence under UV light. Under shortwave, the willemite fluoresces green, while the calcite fluoresces red, for a very nice bight contrast. Under midwave, the willemite turns yellow, and the calcite dims quite a bit. Finally, under longwave UV, the willemite fluoresces bright yellow, with yellow afterglow, but not much from the calcite.

This material seems to have come to the market in late 2023. I bought this piece at a mini mineral show in December 2023 in the San Francisco Bay area from Mike Keim (Marin Minerals). He had almost two flats; I got the best one (in my opinion). Mike brought the same flat at the Tuscon Show at Mineral City in 2024, and a group of fluorescent mineral collectors bought the remaining good pieces. Hopefully more will come to the market!

From: Gotala, Mindouli District, Pool Department, Republic of the Congo.
A cabinet piece: 9 x 7 x 4 cm, 178 g.
MinID: A5N-31C

Longwave & Midwave Shortwave