Sec. III, Ch. 4: The Saffire

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	190 The Sapphire.

	is a dark, friable slate, broken through by eruptive dykes, in some places hornblendic and dioritic, in other places quartzose. At one point near the river, the dykes appear to be trachytic and porphyritic, with amygdules and dark mica. At other points the dykes are more like grey lava. Prof. H. A. Miers, has described one of the dykes as a mica-augite-andesite. The dykes contain Sapphires, Garnets, and other minerals, in well-defined crystals and in rounded masses. It is evident that the denudation of these dykes has set free the Sapphires, and other stones, now found loose in the gravels with the gold. Sapphires have recently been discovered at Yogo Gulch, on the Judith River, and elsewhere near Utica, in Montana. Some of the Yugo Gulch stones are of deep colours, including cornflower and peacock blue. Their mode of occurrence has been described by Mr. Kunz, whilst the character of the crystals has been studied by Mr. Pratt. The Sapphires have been traced to certain igneous dykes composed of a rock recognized by Mr. Pirsson as a dark basic larnprophyre, and he believes that the Sapphires were actually formed in this rock as a true matrix.

	*AUSTRALIAN SAPPHIRES.* The Sapphire is found in many parts of Australia, but the stones are usually of too dark a colour to be of value for jewellery. In the wide-spread auriferous drifts of the goldfields of Victoria, the Sapphire is by no means an uncommon mineral. Probably it has here been derived from the basaltic rocks which, by their disintegration have yielded most of the constituents of the gold-bearing gravels. The Sapphire is also widely distributed in New South Wales, especially in the New England district, where it

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