Morphology of chiolite twins from the Morefield mine, Amelia County, Virginia

Well-formed twinned crystals of chiolite to 3 mm long have recently been fo und in replacement bodies in pegmatitic granite at the Morefield mine, Amel ia County, Virginia. Crystals are composed primarily of the forms {011} and {017}(?), and are invariably twinned on {011}. The twins range from subequ ant to elongate, and from relatively simple contact twins to complex penetr ation twins with hourglass- or S- or L-shaped cross-sections. Untwinned cry stals have not been seen.