is a relatively rare mineral that is usually black
and may be weakly radioactive if it contains Cerium
(Ce), Lanthanum (La), Neodymium (Nd) and Yttrium (Y).
is available from several localities worldwide: Ytterby,
Sweden; ResarÄo Island and elsewhere in Norway; Val
Bedretto, Ticino, Switzerland; Badgastein, Salzburg,
Austria; Loughborough Township, Frontenac County, Ontario,
Canada. In the USA, in the Clear Creek pegmatite,
Llano County, Texas; near Hackberry, Mohave County,
Arizona; near Lake George, Park County, Colorado.