Re-entrant angle.Many crystals are twinned, a process resulting from the growth changing orientation
Re-entrant angle.Many crystals are twinned, a process resulting from the growth changing orientation, and two crystals grow together, but are optically separate. Where the two crystals meet, an angle is often visible, recording how it precipitated from its mother ichor. This example occurs in a crystal of tourmaline in a quartz from Brazil.LozImage credit: Loz -- source link
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