Basanite n. : Lydian stone, or black jasper, a variety of siliceous or flinty slate, of a grayish or bluish black color. It is employed to test the purity of gold, the amount of alloy being indicated by the color left on the stone when rubbed by the metal.

Example:


Taxonomy
Basanite, SiO2, free encyclopedia, Na2O, K2O, jasper, augite, titanium oxides, search, statue, volcanic, mineral, assembly, iron, alkali feldspar, the matrix, basalts, Robert J. Tracy.

Defination from the web:
basanite has been used occasionally to refer to the mineral jasper, for example a black flinty or cherty jasper found in several New ... (2003) Geochemistry and Petrology of a Miocene Trachyte-Basanite Suite from Mt. Tsaratanana, Northern Madagascar, Abstract. Mindat data ...