A dark, fine-grained volcanic rock (phonolite) that resembles basalt; also, a touchstone used in assaying precious metals.
From Greek 'basanites' (test stone), derived from 'basanos' (test or touchstone). In mineralogy, the term refers to specific volcanic rocks with similar fine-grained, dense characteristics.
Basanite was literally the original 'testing ground' for purity—ancient gold merchants carried basanite tablets and scratched precious metals against them to see if they were the real deal.
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