Reederite-(Y) is a rare mineral with the formula (Na,Mn,Fe)15(Y,REE)2(CO3)9(SO3F)Cl.
"REE" in the formula stands for rare earth elements other than yttrium, that is mostly cerium, with traces of neodymium, dysprosium, lanthanum and erbium.
The formula also includes a Levinson suffix "-(Y)" pointing to the dominance of yttrium at the corresponding site.
Reederite-(Y) crystallizes in the hexagonal crystal system with the space group P6, rarely seen among minerals.
This article about a specific carbonate mineral is a stub.