Florencite-(Sm)

Florencite-(Sm)
General
Category Phosphate mineral
Formula
(repeating unit)		 SmAl3(PO4)2(OH)6
Crystal system Trigonal
Crystal class Hexagonal scalenohedral (3m)
H-M symbol: (3 2/m)
Space group R3m
Unit cell a = 6.972, c = 16.182 [Å]; Z = 3
Identification
Color Colorless, pale pink, pale yellow
Crystal habit Sub-mm zones in florencite-(Ce) crystals
Cleavage {0001}, distinct
Fracture Uneven
Mohs scale hardness 5.5-6
Luster Vitreous to greasy
Streak White
Density 3.6 (measured)
Optical properties Uniaxal(+)
Refractive index nω=1.70, nε=1.71
References [1]"Florencite-(Sm) - Handbook of Mineralogy" (PDF). Handbookofmineralogy.org. Retrieved 2016-03-08. [2]

Florencite-(Sm) is a very rare mineral of the plumbogummite group (alunite supergroup) with simplified formula SmAl3(PO4)2(OH)6.[2] Samarium in florencite-(Sm) is substituted by other rare earth elements, mostly neodymium. It does not form separate crystals, but is found as zones in florencite-(Ce),[1] which is cerium-dominant member of the plumbogummite group.[3] Florencite-(Sm) is also a samarium-analogue of florencite-(La) (lanthanum-dominant) and waylandite (bismuth-dominant), both being aluminium-rich minerals.[2]

Occurrence and association

Florencite-(Sm) was revealed in quartz veins in the Maldynyrd Range, Subpolar Urals, Russia. It associates with xenotime-(Y).[1]

Notes on chemistry

Florencite-(Sm) has admixtures of neodymium, and small amounts of cerium, gadolinium, sulfur, strontium, praseodymium, calcium, lanthanum, europium, and silicon.[1]

References

  1. 1 2 3 4 Repina, S.A., Popova, V.I., Churin, E.I., Belogub, E.V., and Khiller, V.V., 2014. Florencite-(Sm)—(Sm,Nd)Al3(PO4)2(OH)6: A new mineral species of the alunite-jarosite group from the Subpolar Urals. Geology of Ore Deposits 53(7), 564-574
  2. 1 2 3 "Florencite-(Sm): Florencite-(Sm) mineral information and data". Mindat.org. Retrieved 2016-03-04.
  3. ↑ "Florencite-(Ce): Florencite-(Ce) mineral information and data". Mindat.org. Retrieved 2016-03-09. l


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