Florencite-(Sm) is a very rare mineral of the plumbogummite group (alunite supergroup) with simplified formula SmAl3(PO4)2(OH)6.
[4] 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),[2] which is cerium-dominant member of the plumbogummite group.
[4] Florencite-(Sm) was revealed in quartz veins in the Maldynyrd Range, Subpolar Urals, Russia.
[2] Florencite-(Sm) has admixtures of neodymium, and small amounts of cerium, gadolinium, sulfur, strontium, praseodymium, calcium, lanthanum, europium, and silicon.