by the accretion of sparse, 2
Plate XVIII (cropped from border and page)
B. Muscovited orthoclase crystal inclosed in fresh orthoclase
Older idiomorphic orthoclase crystal partly altered to fine muscovite and inclosed in fresh, unaltered orthoclase of the second period of consolidation. Drawing from thin section 184, fresh alaskite from the Vega prospect. Illustrates formation of muscovite by the action of the residual magma on earlier formed feldspar during consolidation. Enlarged about 180 diameters.
ex Josiah Edward Spurr (1870-1950 *). Ore Deposits of the Silver Peak Quadrangle, Nevada. USGS Professional Paper No. 55. Series A. Economic Geology, 77; B. Descriptive Geology, 96; D. Petrography and Mineralogy, 33. 1906
University of Michigan copy, digitized February 20, 2010
Nicely aestheticizing wash an artefact of the digitization process.
epigram ex p 103.
8 January 2014
tags: J. E. Spurr; economic geology; magnetite; photo micrographs; rounds