here are twenty-four varieties of Narasimha-salagrama: (1) Laksmi-narasimha
(12) Vidurarana narasimha
(13) Kukushi narasimha
(16) Kapila narasimha
(17) Jvala-narasimha (3 sub-varieties)
The Narasimha salagrama-shilas' generally have four chakras, but sometimes there are only two. They also may have a gaping mouth with sharp teeth like structures. See image of Narasimha salagram above. Here are some descriptions of four specific Narasimha-shilas:
(4) The Kapila-narasimha-salagrama has a large chakra at the place where the tusk would be located; the color of the stone is tawny, and there can be seen on the stone the mark of vanamala. This must be worshipped only by celibates (brahmachari-s) for worldly prosperity (bhukti) or salvation (mukti). (3) The Maha-jvala-nrsimha-murti-salagrama is thick in chape, blue-black in color and has a gaping mouth (aperture). This is fit for worship only by mendicants (mahamuni). (2) The Laksmi-narasimha-salagrama has a cakra on its left side, is black in color, and has spots. Its worship makes for bhukti (worldly prosperity) and mukti (emancipation). (1) The Narasimha-salagrama has an elongated mouth, tawny hued, a longish cakra and a big belly. This stone is suitable for worship by ascetics.