Lewis & Short

băsănītes lăpis = [?BASANITHS (BA/SANOS ?]), a touchstone, test-stone, a very hard stone, used as a test for the precious metals, for whetstones, and, in medicine, for mortars, Plin. 36, 20, 38, § 147; 36, 22, 43, § 157; Isid. Orig. 16, 4, 36.
Also basanites alone, Plin. 36, 7, 11, § 58.