Mineral crystals are of two types. Cystoliths and raphides. Grapefruit-like calcium carbonate is called a cystolith. Cystoliths are present in the leaves of plants like banyan, ash, fig, rubber etc. Needle-like calcium oxalate is called raphide. Plants like Manakchu, Olakchu, Mukhikchu etc. have raphides on their stems and leaves.