A copper-tin alloy containing a sufficiently high percentage of tin (usually about 33%) to form intermetallic compounds in its structure and to cause the alloy to appear white or silvery. Modern speculum metal may contain some zinc. The alloy is hard and brittle but capable of taking a high polish and is therefore satisfactory for reflectors and mirrors. Ancient mirrors made use of similar alloys, usually of beta bronze composition, up to about 24% tin.
