Abstract
PROF. JOHANNSEN has deserved well of petrologists. The present publication by him comprises some half-a-dozen tables, explained and illustrated by notes and diagrams. The minerals are classed in the first place according as they are opaque or transparent, isotropic or uniaxial or biaxial, uncoloured or coloured, and pleochroic or non-pleochroic, and to each of these divisions is allotted a table. In the tables the anisotropic minerals are arranged vertically in the order of their birefringence indicated in the central column; and laterally from the centre outwards, according to their refractive indexes shown at the top of the table. The range of the refractive index of each mineral is given by a horizontal line, somewhat in the same manner as in the “Petrographic Methods “of Dr. Holmes.
Essentials for the Microscopical Determination of Rock-Forming Minerals and Rocks.
By Dr. A. Johannsen. Pp. vi + 53. (Chicago: University of Chicago Press. London: Cambridge University Press, 1922.) 11s. net.
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EVANS, J. Essentials for the Microscopical Determination of Rock-Forming Minerals and Rocks . Nature 111, 143–144 (1923). https://doi.org/10.1038/111143b0
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DOI: https://doi.org/10.1038/111143b0
