. The prospector's field-book and guide in the search for and the easy determination of ores and other useful minerals. the feldspar is in dictinct crystals in compact base,and sometimes lighter than the base, which is fre-quently reddish, purple, or dark green, it is a por-phyritic granite. The granites are sometimes whit-ish, grayish, or flesh-red. They are considered asmetamorphic and not igneous (Dana), althoughsome authors still consider them to be igneous-They always present a crystalline grain in varyingdegrees of fineness and prominence. One form is PREPARATORY INSTRUCTION. 31 given in
. The prospector's field-book and guide in the search for and the easy determination of ores and other useful minerals. the feldspar is in dictinct crystals in compact base,and sometimes lighter than the base, which is fre-quently reddish, purple, or dark green, it is a por-phyritic granite. The granites are sometimes whit-ish, grayish, or flesh-red. They are considered asmetamorphic and not igneous (Dana), althoughsome authors still consider them to be igneous-They always present a crystalline grain in varyingdegrees of fineness and prominence. One form is PREPARATORY INSTRUCTION. 31 given in Fig. 4, from a specimen in the authorspossession. This specimen contains two kinds of mica, oneblack, biotite, the other white, of silvery appearance,muscovite. The biotite presents in spots the appear-ance of hornblende, and only the pen-knife pointshows the scaly lamination of mica under the also contains crystalline forms of potash feldspar(orthoclase), distinguishable from the quartz by theirside only, by the lamellar fracture of its edges, andits peculiar vitreous glimmer, for practically the Fig. Granite with black mica and feldspar crystals, with quartz as chief base. hardness appears the same, although feldspar is ( quartz 7) slightly softer. It would be well forthe prospector to gather many forms of granite andexamine them under the lens until he becomesthroughly used to the variations. The first indications of a deposit possessingeconomic value are, as a rule, to be met with amongthe materials forming the beds of streams, andwherever water-courses have seamed and furrowedthe rocks. Metalliferous deposits should be lookedfor in hilly districts as a general rule, though 32 prospectors field-book and guide. alluvial accumulations may be found in compara-tively flat country. A close study of natural phe-nomena will often help in the discovery of mineralwealth. Thus the form and color of the surface;stained patches; springs of water whether sweet orminer
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectprospec, bookyear1903
