Any of a group of minerals found as brownish-red prismatic crystals in pegmatite veins in Norway and other localities including parts of Canada and California.
Hellandites are hydrous borosilicates of rare earth elements and calcium, also containing aluminium, manganese, and iron, (Ca, REE, Th)₆ (Al, Fe+3) Si₄B₄O₂₂(OH)₄ (where REE = rare earth element). Crystal system: monoclinic.
Early 20th century; earliest use found in Journal of the Chemical Society. From German Hellandit from the name of A. T. Helland, Norwegian geologist + German -it.