...characteristic of this occurrence and often have traces of a blackish crust upon them. Microscopical. In thin section the rock at once shows its character as a...seen in rocks of this class. The biotite is strongly pleocnroic, varying between an almost colorless and a strong, clear, brown tint. It occurs in ragged...

...it as follows: « In thin section the rook nt once shows Its character as a dark, basic lampropbyre. consisting mainly of biotite and pyroxene. There is...seen in rocks of this class. The biotite is strongly pleochroie, varying between nn almost color« Tsehermaks mineral, und petr. Mlttheil., vol. 14. 1894,...

...feldspathoid constituent. In regard to the classification of this rock, Professor Pirsson ™ says : In thin section the rock at once shows its character as a...lamprophyre, consisting mainly of biotite and pyroxene The rock appears to have its closest affinities in the monchiquite group, of which it may be considered...

...feldspathoid constituent. In regard to the classification of this rock, Professor Pirsson " says : In thin section the rock at once shows its character as a dark basic lamprophyre, consisting mainiy of biotite and pyroxene The rock appears to have its closest affinities in the monchiquite group,...

...of a dark grey, basic apiwaranct, and have an uneven fracture. In thin sections it appears as a dark lamprophyre, consisting mainly of biotite and pyroxene. There is a little iron ore present, but much less than is usually seen in rocks of this class. — Electrical measurements by alternating currents,...

...a dark grey, basic api>earance, and have an uneven fracture. In thin sections it appears as a dark lamprophyre, consisting mainly of biotite and pyroxene. There is a little iron ore present, but much less than is usually seen in rocks of this class. — Electrical measurements by alternating currents,...