Variscite , Crandallite Locality: Little Green Monster Variscite Mine, Clay Canyon, Fairfield , Oquirrh Mts, Utah County , Utah , USA ( Locality at mindat.org ) Size: 7.8 x 7.3 x 0.4 cm. A gorgeous slab, polished on both sides, with very intricate patterns of the green and yellow phosphates, variscite and crandallite from the famous Utah locality of the Little Green Monster Variscite Mine. The yellow crandallite surrounding the variscite has exceptional banding. There is also a bit of white wardite. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Crandallite
A calcium-aluminium phosphate named for Milan Crandall Jr. — a common secondary mineral in phosphate deposits and laterites.
Intro adapted from Wikipedia (CC BY-SA).
Crandallite is an IMA-recognized mineral species in the phosphate class, with the chemical formula CaAl₃(PO₄)(PO₃OH)(OH)₆.
It crystallizes in the hexagonal crystal system (space group R-3m). It is a member of the Alunite-crandallite structural group.
Key properties: Mohs hardness 5; specific gravity 2.78–3.04; White streak; Vitreous, dull to chalky when massive luster; optically uniaxial.
IMA symbol Cdl, IMA status: approved, named in 1917.
Found in weathered phosphatic aluminous sedimentary rocks and carbonatites. In phosphate-rich nodules; from complex granite pegmatites; in amphibolite-grade metaquartzites.
It is found associated with Fluorapatite, hydroxylherderite, quartz.
The mineral was named to honor Milan L. Crandall, Jr., mining engineer, of Provo, Utah, USA.