What does epidote mean?
Epidote is a green to yellowish-green silicate mineral composed of calcium, aluminium, iron, silicon, oxygen, and hydrogen, best known for its characteristic pistachio colour. It forms elongated, prismatic crystals and occurs widely in low- to medium-grade metamorphic rocks such as greenschists and in altered igneous rocks, where it commonly fills veins and cavities alongside quartz and calcite. In geological parlance, the name also designates a small group of structurally related minerals. Because it signals particular pressure–temperature conditions during rock formation, epidote is valuable to geologists reconstructing a region's metamorphic history. The word derives from the Greek epididonai, meaning 'to give in addition' — a reference coined by the French mineralogist Haüy around 1801, alluding to the way the crystals enlarge at one end. Though technical rather than everyday vocabulary, epidote appears frequently in field guides, museum labels, and lapidary contexts.
nounA green to yellowish-green mineral consisting of a hydrous calcium aluminium iron silicate, commonly occurring in metamorphic rocks and often found as elongated prismatic crystals.
- A green to yellowish-green hydrous calcium aluminium iron silicate mineral common in low- to medium-grade metamorphic rocks, typically occurring as elongated prismatic crystals.
"The geologist identified the pistachio-green crystals lining the vein as epidote."
"Thin seams of epidote stained the fractured granite a distinctive pistachio green."
"Collectors prize the well-formed prismatic epidote crystals from Pakistan's alpine clefts."
Used when referring to individual crystals or occurrences; the uncountable form is preferred when speaking of the mineral as a substance.
"Hand specimens containing well-crystallised epidotes command high prices among collectors."
Named after the Greek for 'to give in addition' because its crystals literally grow longer at one end — a mineral that takes more than it gives back.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of epidote
The name epidote comes from the Greek epididonai, meaning 'to give in addition' or 'to increase'. It was introduced around 1801 by the French mineralogist René Just Haüy, referring to the fact that one end of the mineral's prismatic crystals is typically enlarged relative to the other. The Greek root didonai ('to give') also underlies familiar words such as dose, antidote, and anecdote, making them distant cognates.
How epidote is actually used
A technical term used chiefly in mineralogy, petrology, and among gem and mineral collectors; rarely encountered in everyday speech. The name is also used for a group of related minerals sharing the same crystal structure.
Easily confused with epidote
Though both begin with 'epi-', epitome means 'a perfect example or summary', while epidote is a green silicate mineral; the two are unrelated in meaning.