שָׁמִיר shâmîyr (H8068)

a thorn; also (from its keenness for scratching) a gem, probably the diamond

1) thorn(s), adamant, flint 1a) thorns, thorn-bushes 1b) adamant (as sharp) 1c) a sharp stone, flint 1c1) perhaps a diamond

from שָׁמַר (H8104) in the original sense of pricking;