Strong's #306: 'achlamah (pronounced akh-law'-maw)

perhaps from 2492 (and thus dream-stone); a gem, probably the amethyst:--amethyst.

Brown-Driver-Briggs Hebrew Lexicon:

'achlâmâh

1) amethyst, a gem in the third row on the ephod, breastplate of judgment worn by the high priest. Transliteration of the Septuagint word. Identification is not certain but is a purple stone perhaps a corundum or red or brown jasper.

Part of Speech: noun feminine

Relation: perhaps from H2492 (and thus dream-stone)

Usage:

This word is used 2 times:

 

Exodus 28:19: "row a ligure, an agate, and an amethyst."
Exodus 39:12: "row, a ligure, an agate, and an amethyst."