Garudapurana 1.68.31

1.68.31

ṣaṭkoṭi śudvamamalaṃ sphuṭatīkṣṇadhāraṃ varṇānvitaṃ laghu supārśvamapetadoṣam /
indrāyudhāṃśuvisṛticchuritāntarikṣamevaṃvidhaṃ bhuvi bhavetsulabhaṃ na vajram //

Endowed with six points, pure, spotless, with clear, sharp edges, rich in colour, light, with good facets, and free from defects,
such a diamond, streaking the sky with rainbow rays, is not easily obtained on earth.