idiochromaticadj.
/ˌɪdɪə(ʊ)krə(ʊ)ˈmatɪk/, U.S. /ˌɪdioʊkrəˈmædɪk/, /ˌɪdiəkrəˈmædɪk/ Mineralogy.
Of a mineral: deriving its colour or optical properties from the chemicals which are an essential part of its composition. Cf. allochromatic adj.
ΚΠ
1849 J. Nicol Man. Mineral. i. ii. 66 Some minerals are naturally coloured, or idiochromatic, showing, in an all modes of their occurrence, a very determinate colour, which may therefore be regarded as essential to them.
1879 Jrnl. Chem. Soc. 36 252 It was supposed that the colorations were due to the presence of impurity... however, it has been found that the colorations are idiochromatic.
1904 Bull. U.S. Geol. Surv. No. 235. 167 The glassy groundmass is in part idiochromatic; in part colorless of itself, but it is completely filled with the greenish chloritic dust, which colors it pale green.
1972 J. A. Beckwith Gem Minerals Idaho 80 Three brightly colored idiochromatic minerals of the copper family having gem interest occur in Idaho.
2000 A. Bartecki & J. Burgess Colour Metal Compounds vii. 165 In the case of idiochromatic colours, transition metal compounds are the principal or dominant component determining the colour of the mineral.
This is a new entry (OED Third Edition, September 2012; most recently modified version published online March 2022).
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adj.1849