| 释义 |
pleochroic, a. Cryst.|pliːəʊˈkrəʊɪk|
[f. pleo-, pleio- + Gr. χρώς complexion, colour, -χρο-ος coloured + -ic: cf. dichroic.]
Showing different colours when viewed in two or in three different directions (dichroic or trichroic), as certain double-refracting crystals. pleochroic halo, each of a series of concentric dark-coloured circles seen in sections of certain minerals and having a radioactive inclusion at their centre; usu. pl.
1864Webster, Pleochroic. 1868Dana Min. (ed. 5) 212 Epidote... Var..3. Withamite. Carmine-red to straw-yellow: strongly pleochroic; the colour as seen through in one direction, deep crimson, in another transverse, straw-yellow. 1894Naturalist 68 Pleochroic haloes, surrounding minute zircon crystals, are seen in both micas. 1909F. P. Mennell Introd. Petrol. ix. 57 ‘Pleochroic halos’..often occur round crystals so small as otherwise to pass unnoticed. 1926R. W. Lawson tr. Hevesy & Paneth's Man. Radioactivity xxvi. 216 (heading) Age determination from the intensity of coloration of pleochroic haloes. 1972M. H. Battey Mineral. for Students iii. 93/2 Small crystals of zircon, containing thorium, embedded in biotite, may by their α-radiation produce an intensely pleochroic halo round the zircon grain.
So pleochroism |pliːˈɒkrəʊɪz(ə)m|, the quality of thus exhibiting different colours; dichroism or trichroism; pleochroitic |-krəʊˈɪtɪk| a. [irreg., after dendritic, etc.], of or pertaining to pleochroism: pleochroˈmatic a. [see chromatic] = pleochroic; pleoˈchromatism = pleochroism; pleochroous |pliːˈɒkrəʊəs| a. = pleochroic.
1857Whewell Hist. Induct. Sc. (ed. 3) III. 542 Experiments on the *pleochroism of minerals. 1886Builder 24 Apr., Dichroism, or pleochroism, practically never occurs in crystals belonging to the cubic system.
1879Rutley Stud. Rocks vii. 58 Determining the position of the *pleochroitic maxima.
1864Webster, *Pleochromatic..*Pleochromatism..*Pleochroous. |