Definition of epidote in US English:



  • A lustrous yellow-green crystalline mineral, common in metamorphic rocks. It consists of a hydroxyl silicate of calcium, aluminum, and iron.

    • ‘Large titanite euhedra are abundant along with apatite and zircon, with allanite and epidote less so.’
    • ‘Along the contact zone the limestones were recrystallized into a cloudy white, massive calcite containing grossular, epidote, magnetite, quartz, and tremolite.’
    • ‘Biotite, epidote and clinopyroxene are also occasionally present, whereas garnet is virtually absent.’
    • ‘Attempts to separate hornblende from these diorites to date them failed utterly because of the intensive alteration of the hornblende to chlorite and epidote.’
    • ‘These crystals are associated with chalcopyrite, galena, quartz, calcite, epidote, and chlorite.’
    • ‘Coarse - to fine-granular aggregates and massive epidote are relatively common.’
    • ‘All five rock samples are mineralogically simple, and comprise mainly muscovite, quartz and feldspar with accessory epidote and biotite.’
    • ‘Biotite is sometimes pseudomorphed by chlorite and epidote, and garnet is absent.’
    • ‘Fine lustrous epidote crystals to 15 cm long have been collected at the Julie claim near Hawthorne, Mineral County, Nevada.’
    • ‘Other minerals that are present in this zone include pyrite and epidote.’
    • ‘The sphalerite is associated with needle quartz, microcrystals of yellow-green epidote, and small spheres of a member of the chlorite group.’
    • ‘The matrix is dominantly felsic, but also contains biotite, muscovite, epidote and titanite.’
    • ‘In addition some also contain hornblende and epidote, the latter in part replacing biotite.’
    • ‘Iron was remobilized and limned specular hematite, along with epidote, actinolite/tremolite, and andradite.’
    • ‘The greenish-colored vein averages 2-4 feet in width and is composed of epidote, quartz, and calcite.’
    • ‘Biotite and epidote occur as secondary minerals.’
    • ‘Most such specimens are partially coated with a druse of calcite, epidote, and small, clear needle quartz crystals.’
    • ‘A variety of minerals were deposited in the hollow vesicles, including chlorite, prehnite, quartz, epidote, microcline, and pumpellyite.’
    • ‘Cementation is dominantly by chlorite, with epidote and zeolites also present as cement phases.’
    • ‘Some calcareous veins contain epidote, titanite and apatite.’


Early 19th century: from French épidote, from Greek epididonai ‘give additionally’ (because of the length of the crystals).