Sinkankasite, mineral formula: H 2MnAl(PO 4) 2(OH)·6H 2O, was named after John Sinkankas (1915-2002), noted author and mineral collector, Scripps Institute of Oceanography. It is triclinic; as colorless, bladed to prismatic crystals up to 4 mm in length, often as divergent, radial aggregates and as pseudomorphs after triphlyte crystals; occurs in the Barker pegmatite (formerly Ferguson pegmatite), east of Keystone, South Dakota, and in the Palermo pegmatite, North Groton, New Hampshire.