The angle or tilt of a mineral vein or geological fault from the vertical, measured downward into the Earth.
From Cornish 'had' (to incline) or related Celtic terms used by Cornish miners. The word entered geological vocabulary from mining terminology in the 18th-19th centuries.
Miners developed hundreds of technical terms—'hade' is one that stuck because it precisely describes the slant of ore veins, making it essential for 300+ years of mining.
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