Very small isolated black crystal of the extremely rare Lengenbach mineral gabrielite (IMA 2002-053). Gabrielite is one of the rarest Lengenbach mineral species. Only very few specimens known. After the book "Faszination Lengenbach (2008)" we know that the total number of gabrielite specimens known worldwide was only 2 !! (p.188) Analyzed specimen by EDX and XRD by F.Nestola of Padua. Specimen found in 1993. Official L-Number is L25259. Ex-Dr.T.Raber collection. — Photo: David Hospital · CC BY-SA 4.0
Gabrielite
An extremely rare thallium-silver-copper-arsenic sulfosalt reported in 2002 from Switzerland's famous Lengenbach quarry.
Intro adapted from Wikipedia (CC BY-SA).
Gabrielite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula Tl₂AgCu₂As₃S₇.
It crystallizes in the triclinic crystal system (space group P-1).
Key properties: Mohs hardness 1.5–2; specific gravity 5.41; Blackish red streak; Metallic luster.
IMA symbol Gab, IMA status: approved, named in 2002.
A late-stage mineral in vugs in a hydrothermally-altered dolomitic marble.
It is found associated with Hutchinsonite, hatchite, edenharterite, trechmannite, tennantite, realgar, rathite.
The mineral was named to honor Walter Gabriel (b. 1943) of Basel, Switzerland, a mineral photographer and expert on Lengenbach minerals.