fortification agate

noun

1. an agate, used as a gem, having polygonal banding such that it suggests the plan of a bastion.

Word History and Origins

Origin of fortification agate¹

First recorded in 1880–85

Example Sentences

Its colors are delicately arranged in stripes or bands, or blended in clouds. µ The fortification agate, or Scotch pebble, the moss agate, the clouded agate, etc., are familiar varieties.

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The varying manner in which these materials are arranged causes the agate when polished to assume some characteristic appearances, and thus certain varieties are distinguished, as the ribbon agate, the fortification agate, the zone agate, the star agate, the moss agate, the clouded agate, &c.

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When the deposits in an agate have been formed on a crop of crystals, or on a rugose base, the cross-section presents a zigzag pattern, rather like the plan of a fortress with salient and retiring angles, whence the stone is termed fortification agate.

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I found a piece of granite and a fragment of fortification agate in the sandy bed of the creek.

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