Chloritoid

Chloritoid
Chloritoid

Chloritoid crystal group on matrix from Nuristan Province, Afghanistan (size:6.3 x 3.5 x 3.0 cm)
General
Category Silicate mineral - nesosilicste
Chemical formula (Fe,Mg,Mn)2Al4Si2O10(OH)4
Strunz classification 09.AF.85
Dana classification 52.03.03.01
Crystal symmetry Monoclinic prismatic 2/m or triclinic pinacoidal 1
Unit cell a = 9.50 Å, b = 5.50 Å, c = 18.22 Å; β = 101.9°; Z = 4 or
a = 9.46 Å, b = 5.50 Å, c = 9.15 Å; α = 97.05° β = 101.56° γ = 90.10°
Identification
Color Dark gray, greenish gray, greenish black
Crystal habit

Tabular pseudohexagonal crystals; rosettes, commonly coarsely foliated with foliae

typically curved or bent; also massive
Crystal system Monoclinic or triclinic
Twinning Common on {001}, polysynthetic may be lamellar
Cleavage Perfect on {001}, distinct on {110}; parting on {010}
Tenacity Brittle
Mohs scale hardness 6.5
Luster pearly on cleavage surfaces
Streak White, grayish, or very slightly greenish
Diaphaneity Translucent
Specific gravity 3.46 – 3.80
Optical properties Biaxial (+) or (–)
Refractive index nα = 1.713 - 1.730 nβ = 1.719 - 1.734 nγ = 1.723 - 1.740
Birefringence δ = 0.010
Pleochroism X = olive-green to yellow; Y = grayish blue to blue; Z = colorless to pale greenish yellow
2V angle Measured: 36° to 89°
Dispersion r > v; strong
References [1][2][3]

Chloritoid is a silicate mineral of metamorphic origin. It is an iron magnesium manganese alumino-silicate hydroxide with formula: (Fe,Mg,Mn)2Al4Si2O10(OH)4. It occurs as greenish grey to black platy micaceous crystals and foliated masses. Its Mohs hardness is 6.5, unusually high for a platy mineral, and it has a specific gravity of 3.52 to 3.57. It typically occurs in phyllites, schists and marbles.

Both monoclinic and triclinic polytypes exist and both are pseudohexagonal.[1][2]

It was first described in 1837 from localities in the Ural Mountains region of Russia. It was named for its similarity to the chlorite group of minerals.[2][3]

References

Phosphates Silicates Sulfides Other
Axinite (borosilicate) · Geigerite (arsenate· Manganese nodule (various) · Samsonite (Sulfosalt) · Zincobotryogen (sulfate)

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Look at other dictionaries:

  • Chloritoīd — (Chloritspath), grobkörnige Massen von sein blättriger Textur, dunkelgrün, Härte 5–6, spec. Gewicht 3,5; kommt am Ural vor …   Pierer's Universal-Lexikon

  • Chloritoïd — (Chloritspat), s. Sprödglimmer …   Meyers Großes Konversations-Lexikon

  • chloritoid — ▪ mineral       common silicate mineral, a basic aluminosilicate of manganese, magnesium, and iron. Once thought to be a member of the brittle mica group, chloritoid has been demonstrated to be structurally different; it is further distinguished… …   Universalium

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  • chloritoid — noun A mixed iron, magnesium amd manganese silicate mineral of metamorphic origin, with the chemical formula (Fe,Mg,Mn)AlSiO(OH) …   Wiktionary

  • Chloritoid — Chloritoịd   [k ] der, s, grünes bis schwarzes, monoklines oder triklines Mineral der chemischen Zusammensetzung Fe2+2Al4[(OH)4 | O2 | (SiO4)2], zum Teil manganreich (Ottrelith); Härte nach Mohs 6 6,5, Dichte 3,4 bis 3,6 g/cm3; meist als derbe… …   Universal-Lexikon

  • Chloritoid — Chlo|ri|to|id der; s <zu ↑...oid> ein grünes bis schwarzes Mineral …   Das große Fremdwörterbuch

  • chloritoid — chlo·ri·toid …   English syllables

  • chloritoid — rəˌtȯid noun ( s) Etymology: German, from chlorit chlorite (mineral) + oid : a mineral (Mg1Fe)AlSiAlO5(OH)2 consisting of a silicate of aluminum and ferrous iron with magnesium occurring usually in dull green to gray or grayish black masses of… …   Useful english dictionary

  • Basler Taufstein — Staurolith Chemische Formel (Fe2+,Mg2+,Zn2+,Co2+)4Al18Si8O46(OH)2 Mineralklasse Inselsilikate mit tetraederfremden Anionen (Neso Subsilikate) VIII/B.03 10 (nach Strun …   Deutsch Wikipedia

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