Agate

Agate is one of the gemstones the Bible mentions by name. It is set in the third row of the high priest’s breastplate, between a ligure and an amethyst. Isaiah promises a restored city whose windows will be of agates, with gates of carbuncles and borders of pleasant stones. Ezekiel lists it among the goods that merchants of Syria brought to the markets of Tyre, alongside emeralds, coral and fine linen. So it appears as something sacred, something promised and something sold. A look at Exodus 28 shows the whole breastplate and its stones.

3 verses

Exodus

Exodus 28:19

And the third row a ligure, an agate, and an amethyst.

Isaiah

Isaiah 54:12

And I will make thy windows of agates, and thy gates of carbuncles, and all thy borders of pleasant stones.

Ezekiel

Ezekiel 27:16

Syria was thy merchant by reason of the multitude of the wares of thy making: they occupied in thy fairs with emeralds, purple, and broidered work, and fine linen, and coral, and agate.

From Easton's Bible Dictionary

Matthew George Easton, 1897

(Heb. shebo), a precious stone in the breast-plate of the high priest (Ex. 28:19; 39:12), the second in the third row. This may be the agate properly so called, a semi-transparent crystallized quartz, probably brought from Sheba, whence its name. In Isa. 54:12 and Ezek. 27:16, this word is the rendering of the Hebrew cadcod, which means “ruddy,” and denotes a variety of minutely crystalline silica more or less in bands of different tints.

This word is from the Greek name of a stone found in the river Achates in Sicily.

From Smith's Bible Dictionary

William Smith, 1884

a beautifully-veined semi-transparent precious stone, a variety of quartz. Its colors are delicately arranged in stripes or bands or blended in clouds. It is mentioned four times in the text of the Authorized Version, viz., in (Exodus 28:19; 39:12; Isaiah 54:12; Ezekiel 27:16) In the two former passages; where it is represented by the Hebrew word shebo it is spoken of as forming the second stone in the third row of the high priest’s breastplate; in each of the two latter places the original word is cadced , by which, no doubt, is intended a different stone. [RUBY] Our English agate derives its name from the Achates, on the banks of which it was first found.