Definition, synonyms and related words
A trigonal-ditrigonal pyramidal mineral containing aluminum, calcium, chlorine, fluorine, hafnium, hydrogen, iron, manganese, niobium, oxygen, potassium, silicon, sodium, strontium, tantalum, titanium, yttrium, and zirconium, as well as lanthanum, cerium, praeseodymium, neodymium, and samarium.