The Quarterly journal of the Geological Society of London . Some of the smallest of the spheroids, however, are varioliticthroughout. AVhen examined under the microscope with a lowpower, the rock is seen to consist of a thick green groundmass,containing a number of round white varioles, sharply marked off In both occur small circular vesicles filled from the groundmass VARIOLITIC DIABASE OF THE FICHTELGEBIRGE. 49 with chlorite, and a large number of irregular spaces of a slightlydichroic, transparent material. Under a higher power, though therock is greatly decayed, the principal points in str
The Quarterly journal of the Geological Society of London . Some of the smallest of the spheroids, however, are varioliticthroughout. AVhen examined under the microscope with a lowpower, the rock is seen to consist of a thick green groundmass,containing a number of round white varioles, sharply marked off In both occur small circular vesicles filled from the groundmass VARIOLITIC DIABASE OF THE FICHTELGEBIRGE. 49 with chlorite, and a large number of irregular spaces of a slightlydichroic, transparent material. Under a higher power, though therock is greatly decayed, the principal points in structure can bedetermined. The groundmass is resolved into three constituents:there is a greenish, isotropic matrix, the transparency of which isdiminished by a dust of minute opaque grains ; it also contains acrowd of small granules and crystals; in most cases these arecertainly augite, and it is probable the whole series are of thismineral. Occasionally a few fine felspar needles occur iu thegroundmass, and sometimes these are grouped into radial clusters
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Keywords: ., bookcentury1800, bookdecade1840, bookidquarte, booksubjectgeology
