Resembling or having the qualities of adamant; hard, unyielding, or diamond-like.
From Greek 'adamant' (unbreakable stone/diamond) + '-oid' (resembling), literally meaning 'diamond-like' in appearance or hardness.
The term 'adamantoid' was especially popular in older scientific texts to describe very hard minerals, but it's fallen out of favor because geologists realized that actual hardness is better measured by specific scales like Mohs hardness.
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