A lustrous yellow, green, or black mineral, Ca2(Al, Fe)3(SiO4)3OH, commonly found in metamorphic rock.
[French épidote, from Greek epididonai, to give in addition, increase (from the greater length of its crystals compared with those of related minerals) : epi-, epi- + didonai, to give; see dō- in the Appendix of Indo-European roots.]
ep′i·dotic (-dŏtĭk) adj.
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