Calcite.

Calcite.

Nantiago mine, Central Wales orefield. The uncommonly flat bladed crystals of calcite are deposited on a piece of host rock of indeterminate nature. This type of crystal is more usually associated with barite, which I don't think has been recorded at this mine. The gangue mineral at Nantiago is calcite, and the spoil heaps are littered with the mineral, mostly displaying it's rhombohedral habit.