touch-stone Copy link Outline I. Lit.1. cōtĭcŭla2. lapis Heraclius Lydius3. index, ĭcis, m.4. *schistus LydiusII. Fig. • touch-stone: I. Lit.: 1. cōtĭcŭla: Plin. 33, 8, 43. 2. lapis Heraclius Lydius: ib. 3. index, ĭcis, m.: Ov. Met. 2, 706. 4. *schistus Lydius: Linn. Phr.: after applying the t., postquam indicium est factum, Vitr. 9, 3. II. Fig.: obrussa (a testing of gold): reason must be used as a t., adhibenda tanquam obrussa ratio, Cic. Brut. 74, 258: to apply the t. to arguments, argumenta ad obrussam exigere, Sen. Q. N. 4, 5.