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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1859 Excerpt: ...of felspar that are particularly rich in lime. In the dioritic or albitic hornblende rocks, the amount of albite is sometimes so small that they are almost mere hornblende rocks, and sometimes albite is altogether wanting. In others, on the contrary, the hornblende is present only in very small proportion. Among the accessory constituents of these rocks are quartz, mica, garnet, epidote, magnetic oxide of iron, and iron pyrites. In hornblende slate--amphibolite--quartz, felspar, hornblende, etc., sometimes occur in nests or as veins, and other minerals in drusy cavities. Hornblende slate occurs very frequently, and it generally presents very distinct stratification. Diorite is also of frequent occurrence as a massive rock, especially in the Ural, though it does sometimes present more or less distinct stratification. Transitions into hornblende rocks are very frequent phenomena, so that whatever is true with regard to one rock also applies to the other. With regard to epidote, which occurs as a parasitic mineral almost everywhere that ferruginous minerals undergo decomposition, it is met with in hornblende rocks under circumstances similar to those observed in melaphyr.f Perhaps in the former case, as well as in the latter, a similar connection between epidote and quartz exists, for in the conversion of hornblende into epidote, Naumann.--Lelirb. d. Gcognosie, i, 579, et seq. t See ante, p. 229. as it is in the decomposition of melaphyr into epidote, quartz would be eliminated. If future examination should point out the association of albite with epidote, it might be inferred that even during the alteration, albite was removed or reproduced. The possibility of this must be admitted, for I found in the Berlin collection of minerals a specimen from Arendal in w...

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