May 14 2014
Chlorotoid is a silicate mineral that was first described in 1837, from the Ural Mountains region of Russia. It was named for its similarities of the chlorite-group minerals.
Properties of Chloritoid
The following are the key properties of Chloritoid:
- Cell Data
- Space Group: C2/c
- a = 9.50(3)
- b = 5.50(2)
- c = 18.22(5)
- β = 101°57(5)'
- Z = 4
Or
- Space Group: C1
- a = 9.46(1)
- b = 5.50(1)
- c = 9.15(1)
- α = 97:05(2)°
- β = 101:56(2)°
- γ = 90:10(2)°
- Z = 4
- Crystal Data
- Monoclinic or triclinic, both pseudohexagonal
- Point Group: 2/m or 1
- Rarely as rosettes of pseudohexagonal tabular crystals; commonly coarsely foliated with foliae
- typically curved or bent; massive
- Twinning: Common on {001}, may be lamellar; twin axes [100], [110], and [130] observed
- X-ray Powder Pattern: 4.498 (100), 4.449 (100), 2.963 (90), 1.5813 (80), 2.367 (70), 2.306 (70), 2.639 (50)
- Chemical Composition
| Elements |
Content |
| Al2O3 |
40.12 |
| FeO |
27.06 |
| SiO2 |
23.91 |
| H2O+ |
7.03 |
| Fe2O3 |
1.23 |
| MgO |
0.51 |
| TiO2 |
0.20 |
| MnO |
0.16 |
| CaO |
0.04 |
| F |
0.01 |
| H2O- |
0.01 |
| K2O |
trace |
| Total |
100.28 |
- Optical Properties
- Optical Class: Biaxial (+) or (-)
- Pleochroism: X = olive-green to yellow; Y = grayish blue to blue; Z = colorless to pale greenish-yellow
- Orientation: X or Y = b (monoclinic)
- Z ^ c = 2°-30°
- Y ˜ b (triclinic)
- Dispersion: r > v; strong
- α = 1.705-1.730
- β = 1.708-1.734
- γ = 1.712-1.740
- 2V(meas.) = ∼45°-70°
- Estimated Properties
| Electron density |
Bulk density (electron density) = 3.43 g/cm3
note: Specific gravity of Chloritoid = 3.47 g/cm3 |
| Photoelectric |
PEChloritoid = 5.82 barns/electron
U = PEChloritoid x ρElectron density = 19.95 barns/cm3 |
| Fermion index |
Fermion index = 0.01
Boson index = 0.99 |
Radioactivity
|
Chloritoid is not radioactive
|
How to Identify Chloritoid
Chloritoid is non-fluorescent and occurs in a range of colors, from dark gray to dark green, grayish-black, green-black, and green-gray. It has a transparent to translucent appearance, with pearly luster and green-gray streak. Its fractures are brittle, like that of non-metallic minerals and glasses. It exhibits two-dimensional platy forms, or massive crystal forms.
The hardness of the mineral is 6.5, and its average density is 3.54 g/cm3.
Global Distribution
Chloritoid is distributed in the following places:
- Kosoi Brod, Mramorskii Zavod, south of Yekaterinburg, Russia
- Salmchateau, near Ottre, Ardennes Mountains, Belgium
- Nadels and Zermatt, Valais, Switzerland
- PrÄagraten, Tirol, Austria
- Along the coast between Stonehaven and Aberdeen, Scotland
- Tintagel, Cornwall, England
- Natick, Kent Co. Rhode Island, USA
- Chester, Hampden Co. Massachusetts
- Clove Valley, Duchess Co. New York
- Bull Mountain, Patrick Co. Virginia
- Chibougamau and St. Giles, Quebec, Canada
- Kalgoorlie, Western Australia.
Occurrence of Chloritoid and Useful Mineral Association
Chloritoid occurs in regionally metamorphosed pelitic sediments, lower grade staurolite zones, garnet, schists in the biotite, quartz-carbonate veins, and other hydrothermal environments.
References