Two Yttrium Minerais: Spencite and Rowlandite1

fro11 1 pegmatite in Cardiff township, Haliburton County, Ontario. Found as dark reddish brown to brownish black anhedral masses. Hardneis B$, specific gravity 8,08. Metamict; isotropic with n near 1.630. when the mineral is heated at 925" i the n increases to about 1.640 and the specific gravity to 8.20. At high temperatures the mineral decomposes before it recrystallizes and r-ray difiraction daticannol be obtained. spencite is related chemically to the minerals of the Datolite Group and may be isostructural with them. It is named after the canadian mineralogist Hugh s. Spence. A re-examination of the little known mineral rowlandite from Baringer Hiil, Texas, establishes it as a valid species. Composition near (y, Fe, Ce)s(SiOa)r(F, 0H). Metamict; with n 1.704. Hardness 5$, specific gravity 4.Bg; *-ray powder data are given foi material recrystallized in nitrogen at 900" c (with tnean n 1.76, specific gravity a.65).