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

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
"Florencite-(Sm): Florencite-(Sm) mineral information and data". Mindat.org. Retrieved 2016-03-04.
"Florencite-(Ce): Florencite-(Ce) mineral information and data". Mindat.org. Retrieved 2016-03-09.l

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[GOD-1] 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

[Mindat-2] "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