The base is generally a finely granular mixture of the same elements
which occur in the larger imbedded
p 253
crystals. In granitic porphyry that is very poor in quartz, the feldspathic
base is almost granular and laminated.*
[footnote] *Dufrenoy et Elie de Beaumont, 'Geologie de la France', t. i.,
p. 130.
3. 'Greenstones, Diorite', are granular mixtures of white albite and
blackish-green hornblende, forming dioritic porphyry when the crystals are
deposited in a base of denser tissue. The greenstones, either pure, or
inclosing laminae of diallage (as in the Fichtelgebirge), and passing into
serpentine, have sometimes penetrated, in the form of strata, into the old
stratified fissures of green argillaceous slate, but they more frequently
traverse the rocks in veins, or appear as globular masses of greenstone,
similar to domes of basalt and porphyry.*
[footnote] *These intercalated beds of diorite play an important part in
the mountain district of Nailau, near Steben, where I was engaged in mining
operations in the last century, and with which the happiest associations of
my early life are connected. Compare Hoffmann, in Poggendorf's 'Annalen',
bd. xvi., s. 558.
'Hypersthene rock' is a granular mixture of labradorite and hypersthene.
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