clinohumite
Clinohumite is an uncommon member of the humite group, a magnesium silicate according to the chemical formula (Mg, Fe)9(SiO4)4(F,OH)2. The formula can be thought of as four olivine (Mg2SiO4), plus one brucite (Mg(OH)2). Indeed, the mineral is essentially a hydrated olivine and occurs in altered ultramafic rocks and carbonatites. Most commonly found as tiny indistinct grains, large euhedral clinohumite crystals are sought by collectors and occasionally fashioned into bright, yellow-orange gemstones. Only two sources of gem-quality material are known: the Pamir Mountains of Tajikistan, and the T
Key facts
- Mineral.name
- Clinohumite
- Mineral.image
- File:Clinohumite.jpg
- Mineral.category
- Nesosilicate
- Mineral.formula
- (Mg,Fe)9(SiO4)4(F,OH)2
- Mineral.IMAsymbol
- Chu
- Mineral.system
- Monoclinic
- Mineral.class
- Prismatic (2/m) (same H-M symbol)
- Mineral.symmetry
- P21/c
- Mineral.unit cell
- a = 13.71 Å, b = 4.75 Å, c = 10.29 Å; β = 100.83°; Z = 2
- Mineral.color
- Brownish to orange, yellow, red
- Mineral.habit
- Granular, prismatic, twinned
- Mineral.twinning
- Simple, lamellar common on {100}
Article
5 sectionsContents
- Properties
- Formation and occurrence
- Crystal structure
- See also
- References
{{Infobox mineral | name = Clinohumite | image = File:Clinohumite.jpg | category = Nesosilicate | formula = (Mg,Fe)9(SiO4)4(F,OH)2 | IMAsymbol=Chu | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = P21/c | unit cell = a = 13.71 Å, b = 4.75 Å, c = 10.29 Å; β = 100.83°; Z = 2 | color = Brownish to orange, yellow, red | habit = Granular, prismatic, twinned | twinning = Simple, lamellar common on {100} | cleavage = Poor on {100} | fracture = Subconchoidal to uneven | mohs = 6 | luster = Vitreous to resinous | refractive = nα = 1.623 – 1.702 nβ = 1.636 – 1.709 nγ = 1.651 – 1.728 | opticalprop = biaxial (+) | birefringence = +0.028 | 2V = Measured: 52° to 90° | pleochroism = X = golden yellow, yellow-brown, deep reddish yellow; Y = pale yellow, yellow-orange, light yellow; Z = pale yellow, yellow-orange, colorless | streak = White | gravity = 3.17–3.35 | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Transparent to translucent | other = | var1 = Titanclinohumite | var1text = Titanoan; (Mg,Fe2+,Ti)9 [(F,OH,O)2|(SiO4)4]
| references = }}