Triplite

Triplite
Triplite from Alchuri, Shigar Valley, Baltistan, Pakistan (1.2 × 1 × 0.9 cm)
General
CategoryPhosphate minerals
Formula
(repeating unit)
(Mn,Fe)2(PO4)(F,OH)
IMA symbolTrl[1]
Strunz classification8.BB.10
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupI2/a (no. 15)
Unit cella = 11.97 Å, b = 6.52 Å
c = 10.09 Å; β = 105.62°; Z = 8
Identification
ColorChestnut to reddish brown, flesh-red, salmon-pink
Crystal habitPrismatic, massive to nodular
CleavageGood on {001}, fair on {010}, poor on {100}
FractureUneven to subconchoidal
Mohs scale hardness5 to 5.5
LusterVitreous to resinous
StreakWhite to brown
DiaphaneityTranslucent to opaque
Specific gravity3.5 – 3.9
Optical propertiesBiaxial (+)
Refractive indexnα=1.643–1.684, nβ=1.647–1.693, nγ=1.668–1.703
PleochroismDistinct; yellow-brown to reddish brown
2V angle25 – 76°
Dispersionr > v, moderate to strong
Alters toAlters to brownish black
References[2][3][4][5]

Triplite is a rare phosphate mineral with formula: (Mn, Fe)2PO4(F, OH). It occurs in phosphate-rich granitic pegmatites typically as irregular brown opaque masses. Triplite was first described in 1813 for an occurrence in Chanteloube, Limousin, France.[6] The name is from the Greek triplos for triple, in reference to the three cleavage directions.[3] In color and appearance, it is very similar to rhodocrosite, another manganese bearing mineral. Chemically, it is also quite similar to triploidite the difference being that triplite is fluorine dominant while triploidite is hydroxide dominant.

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Handbook of Mineralogy
  3. ^ a b Mindat.org
  4. ^ Webmineral data
  5. ^ Vignola, Pietro; Gatta, G. Diego; Hatert, Frédéric; Guastoni, Alessandro; Bersani, Danilo (April 2014). "ON THE CRYSTAL-CHEMISTRY OF A NEAR-ENDMEMBER TRIPLITE, Mn 2+ 2 (PO 4 )F, FROM THE CODERA VALLEY (SONDRIO PROVINCE, CENTRAL ALPS, ITALY)". The Canadian Mineralogist. 52 (2): 235–245. doi:10.3749/canmin.52.2.235.
  6. ^ Triplite Crystals from Colorado, C. W. Wolf and E. Wm. Heinrich, American Mineralogist, Volume 32, pages 518–526, 1947