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The Pamphlet Collection of Sir Robert Stout: Volume 67

Materials ejected

Materials ejected.

Two different rocks have been ejected—viz., rhyolite and augite-andesite—and each is either compact or vesicular. The augite-andesite, when compact, is greyish-black, vesicular in places, and with opaque-white angular fragments of decomposed rhyolite. In the vesicular state it is black scoria.

The rhyolite is of several varieties, but all are pale in colour, and more or less decomposed by the felspar being kaolinized. In page 14 the vesicular state it is white glassy pumice, with quartz grains more or less abundantly developed.

From the mountain came vesicular scoria and pumice as well as fine ash. It always fell dry, and was hot eighteen miles from the mountain. Scoria is far more abundant than pumice.

From the plains came compact blocks, grit, and dust, chiefly rhyolite, without any pumice or scoria. These fell warm close round the openings, but farther off as intensely cold mud, and still farther as fine dry dust.

The boundary between these two deposits is tolerably well marked, and passes along the western base of Mount Tarawera through the eastern end of Rotoiti to Maketu. To the east of this line the deposit is all from the mountain, while to the west the deposit from the mountain is overlain by the deposit from the craters on the plains.