Mineral Information and Data:

Clinohumite
Mg9(SiO4)4F2 [CNMNC approved formula]

Named in allusion to its monoclinic crystal structure and relationship to humite, which was named after Sir Abraham Hume (1749-1838), English connoisseur and collector of gems, minerals and artwork.

IMA status : Valid species (Pre-IMA 1876) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
52.03.02d.01  
  (52) Nesosilicate Insular SiO4 Groups and O, OH, F, and H2O
  (52.03) with cations in [6] coordination only
  (52.03.02d) Humite group (Clinohumite series)
  
Nickel-Strunz
(10th edition) :
09.AF.55
  (09) Silicates
  (09.A) Nesosilicates (Isolated tetrahedron) structures
  (09.AF) Nesosilicates with additional anions; cations in [4], [5] and/or only [6] coordination
  
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 13.71Å, b = 4.75Å, c = 10.29Å, β = 100.83°
Crystal Habit: Crystals varied, highly modified; lamellar
Twinning: Common on {100}, simple, lamellar
  
Color: Yellow, brown, white
Diaphaneity: Transparent to translucent
Luster: Vitreous
Hardness (Mohs): 6
Measured Density: 3.17 to 3.35 g/cm3
Cleavage: 1; {100} indistinct
Tenacity: Brittle
Fracture: Uneven to conchoidal
  
Geologic Setting: In contact metamorphic zones in dolostones and metasomatized limestones adjacent to felsic plutonic rocks; in serpentine and talc schists; in a carbonatite.
Mineral Association: Grossular, wollastonite, forsterite, monticellite, cuspidine, °uoborite, ludwigite,
dolomite, calcite, talc, biotite, spinel, vesuvianite, sanidine, meionite, nepheline
  
Other Properties: Gemstone Extremely Rare.

 

Clinohumite
Dark redbrown crystals in phlogopite matrix
Origin: Kovdor, Kola Peninsula, Russia
Sample size: 2 x 3 cm matrix
Photo: Diederik Visser

 

Clinohumite
Origin: roadcut between Escouloubre (Dept. Aude) and Usson (Dept. Ariège), France
Sample size: 3 x 4 cm
Photo: Diederik Visser

 

Clinohumite
Origin: Kukh-i-Lal, Pyandzh Valley,Pamir Mountains, Tajikistan
Sample size: 1.0 x 0.9 x 0.6 cm (specimen) and 5 x 5 x 4 mm (gemstone)
Photo: Rob Lavinsky

 

Clinohumite
5 x 5 x 4 mm (gemstone) of above

 

Clinohumite
Origin: Ladjuar Madan, Kokcha Valley, Afghanistan
Sample size: 2.1 x 1.2 x 1 cm
Photo: John Veevaert, Trinity Mineral Co

 

Clinohumite
(zoom-in of above)

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