Calcite

N'Chwaning II Mine, N'Chwaning mining area, Kuruman, Kalahari manganese field (KMF), Northern Cape Province  South Africa

Specimen size: 6.5 × 6 × 4.9 cm = 2.56” × 2.36” × 1.93”
Main crystal size: 4.5 × 2.6 cm = 1.77” × 1.02”