General Information:
Chemical Formula:
(Fe+++,Ti)4Ti3AsO13(OH)
Composition:
(Molecular Weight = 666.95 gm)
Titanium 21.54 % Ti
Iron 33.49 % Fe
Arsenic 11.23 % As
Hydrogen 0.15 % H
Oxygen 33.58 % O
Empirical Formula:
Fe3+4Ti3AsO13(OH)
Environment:
The Fe++ dominant analog of tomichite and the As+++ dominant analog of derbylite. In hydrothermal viens in a two-mica paragneiss.
IMA Status:
Approved IMA (Dana # Added)
Locality:
Larchelitini, in the Monte Leone Nappe, Binntal region, western Alps, Switzerland.
Name Origin:
For Prof. Dr. Stefan Graeser (1935-), in recognition of his extensive research on the oxides and sulfosalts of arsenic in the Binntal region of Switzerland.
Physical Properties:
Cleavage:
[100] Distinct
Color:
black.
Density:
4.62
Diaphaniety:
Opaque
Habits:
Acicular - Occurs as needle-like crystals., Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite), Aggregates - Made of numerous individual crystals or clusters.
Hardness:
5.5 - Knife Blade
Luster:
Metallic
Streak:
black
More details...