Mineral Information and Data:

Tl2O3 [CNMNC approved formula]

Named for the medieval Uzbek (Persian) scholar and physician, Abu ‘Ali al-Husayn ibn ‘Abd Allah ibn Sina (Avicenna) (930–1037), who lived in Bukhara, Tajikistan.

IMA status : Valid species (Pre-IMA 1958) Grandfathered
(8th edition) :  
  (04) Simple Oxides
  (04.03) with a cation charge of 3+ (A+++2 O3)
(10th edition) :
  (04) Oxides and Hydroxides
  (04.C) Metal:Oxygen = 2:3, 3:5, and Similar
  (04.CB) With medium-sized cations
Crystal system: Cubic System
Point group (H-M): m3 (or 2/m 3) — diploidal
Unit cell: a = 10.5468Å
Crystal Habit: As crystals, less than 1 mm, some showing subhedral octahedral faces; as porous grains, and as a coating on carlinite.
Color: Grayish black with brownish black tint; pale to medium gray under reflected light
Diaphaneity: Opaque
Luster: Metallic
Hardness (Mohs): 1.5 - 2.5
Measured Density: 8.9 g/cm3
Tenacity: Very brittle
Fracture: Conchoidal to hackly, uneven
Streak: Grayish black, black with a brownish tint
Geologic Setting: In the weathered zone of a hematite-alcite vein cutting banded marmorized and silicified limestones near a granite-gneiss contact (near Dzhuzumli, Tajikistan); formed by oxidation of carlinite in carbonaceous gold ores in silicified limestones and quartz (Carlin mine, Nevada, USA).
Mineral Association: Hematite, “limonite”, ferruginous clay minerals (near Dzhuzumli, Tajikistan); carlinite, hematite, quartz (Carlin mine, Nevada, USA); parapierrotite (Lookout Pass, Utah, USA).