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It may be necessary to observe that the height of the Cataract of the Macquarie River above the sea, was ascertained by barometrical admeasurement to be 650 feet. The country subsequently traversed is considerably lower. The specimens refer only to the geological formation of the distant interior. Schorl Rock. Colour blueish grey, fine grained, extremely hard. Composed of Tourmaline and Quartz.
A schorl rock, of a blue colour and fine grain, composed of tourmaline and quartz, forms the bed of the Macquarie at the Cataract; and, in immediate contact with it, a mass of mica slate of alternate rose, pink, and white, was observed, which must have been covered by the waters of the river when Mr. Oxley descended it.
After the accounts given by Barrow, Carmichael, Basil Hall, and W.B. Clarke of the geology of this district, I shall confine myself to a few observations on the junction of the three principal formations. In another place, I found crystals of black schorl radiating from a common centre. Dr.
Both specimens immediately succeed the Schorl rock at the Cataract, in large smooth-sided masses. This formation may be said to terminate the rocks connected with the dividing ranges, since it is the last that occurs at their western base. A little below the Cataract, the county undergoes a remarkable change, and becomes extremely depressed. Porphyry with Feldspar.
The quartz predominates in the mass; and is generally of a milky white. I observed neither hornblende, black schorl, nor rutile titanite, in this granite. In some ledges we recognised round masses, of a blackish gray, very quartzose, and almost destitute of mica. They are from one to two inches diameter; and are found in every zone, in all granite mountains.
MICA SCHIST. Pink marble dolomite, on hills of mica schist, of various colours, with trap, schorl in gneiss, kyanite or disthene gneissose mica in the schist. 1500 ft. COAL IN SANDSTONE. Specular and magnetic iron on various igneous rocks; finely laminated porphyry; granite; hot fountain.
Is it quartz, felt-spar, mica, or schorl? or, Was it calcareous? If our author knows any thing about these necessary questions, Why has he not informed us, as minutely as he has done with regard to the dimensions of the mole, with which we certainly are less concerned?
Structurally, therefore, these isles are a continuation of Land's End, but the granite has become less consistent and more friable; it is largely broken into felspar, quartz, and mica, with schorl, chlorite, and hornblende.
It was not till fourteen years after that the body of Clarke was found, and Mrs. Aram declared that her husband and Housman had murdered him; Housman turned King's evidence, and Aram was hung on 16th August 1759. Roche hermitage in Cornwall occupies a spire of rocks of schorl that shoots 100 feet above the surrounding moor.
But in stones, much depends upon the peculiar nature of their constituent parts; when the feldspar of the granite rocks contains little alkali or calcareous earth, it is a very permanent stone; but, when in granite, porphyry, or sienite, either the feldspar contains much alkaline matter, or the mica, schorl, or hornblende much protoxide of iron, the action of water containing oxygen and carbonic acid on the ferruginous elements tends to produce the disintegration of the stone.
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