A superb, isolated crystal of the rare calcium-manganese silicate poldervaartite, from the Kalahari Manganese Fields in South Africa. What makes this specimen really distinctive is the quite rare appearance of a glassy, window-clear crystal of calcite that has grown right up against the poldervaartite. Can be trimmed to a killer thumbnail! The poldervaartite crystal measures 1.8 cm. 5.2 x 2.3 x 2.1cm