Theophrastite is a trigonal-hexagonal scalenohedral emerald green mineral containing nickel, hydrogen, and oxygen. This mineral was named after the first Greek mineralogist Theophrastus.
Properties of Theophrastite
The following are the key properties of theophrastite:
- Cell Data
- Space group: P3m1 (synthetic)
- a = 3.131
- c = 4.608
- Z = 1
- Crystal Data
- Point group: 3 2/m
- Minute crystals- finely parallel fibrous, in botryoidal crusts, to 0.5 cm; crystals may be interstratified with other layer-structure minerals.
- X-ray powder pattern: 2.335 (100), 4.61 (95), 1.755 (50), 2.708 (30), 1.563 (25),1.480 (18),1.336 (10)
- Chemical Composition
- Optical Properties
- Optical Class: Uniaxial (+)
- Birefringence: very weak
- Pleochroism: Weak
- ω = 1.759-1.760
- ε = 1.759-1.760
- Estimated Properties
||Bulk density (electron density)=3.90 g/cm3
note: Specific gravity of theophrastite = 3.93 g/cm3
||PETheophrastite = 24.82 barns/electron
U=PETheophrastite x ρelectron density= 96.81 barns/cm3
||Fermion index = 0.0073
Boson index = 0.9926
|GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Theophrastite is not radioactive
How to Identify Theophrastite
Theophrastite can be identified in the field by emerald green or blue-green color variations. The appearance of this mineral is transparent. It is a mineral with a glassy luster and a light green streak. The conchoidal fractures in the mineral are brittle with smooth curving surfaces. The density of theophrastite is 4 g/cm3 and hardness is 3.5 (approximate to a copper penny).
Theophrastite is widely distributed in the following locations:
- Greece - From the Verrnion district, 50 km west of Thessalonike, Macedonia
- Scotland - In the Hagdale quarry, Unst, Shetland Islands
- Canada - Québec, Estrie, Les Sources RCM, Asbestos Jeffrey mine (Jeffrey quarry; Johns-Manville mine)
- Australia - At the Lord Brassey mine, Heazlewood, Tasmania.
Occurrence of Theophrastite and Useful Mineral Association
Theophrastite is often associated with minerals such as millerite, magnetite, chromite, vesuvianite, chlorite, andradite-grossular, nickeliferous serpentine minerals, calcite (Vermion district, Greece); reevesite, zaratite, honessite, hydrohonessite (Hagdale quarry, Scotland).
Theophrastite occurs as coatings in chromitite in lenses in serpentinites found in Vermion district, Greece and on chromitite in Hagdale quarry, Scotland.