Hornblende schist

Definition and stakes

William O. Crosby Common Minerals and Rocks

Hornblende schist sometimes passes into amphibolite, through the absence of quartz; and so does diorite, when the feldspar is deficient or wanting. Specimen 20, though small, is a typical example of this rock. The physical and chemical characteristics are essentially the same as for the mineral hornblende. The texture varies from coarsely to finely crystalline. The crystals are usually short and thick, and lie in all directions in the rock, which is thus very massive, the schistose texture being entirely wanting, and the stratification rarely showing in small masses.
Source: Gutenberg

John MacCulloch On the Geology of Glen Tilt (1816)

It then assumes an appearance exactly resembling that of hornstone or compact felspar, having a smooth texture, with a thin-edged fracture intermediate between the splintery and flat conchoidal. I may as well add here that the schist is often of an argillaceous, but highly indurated, character, and also that it often passes into hornblende slate, and this (it is worthy of notice) the more frequently as it approximates nearer to the granite.
Source: Wikisource

Portrait of John Ball John Ball The geography and geology of south-eastern Egypt (1912)

Under the heading of hornblende-schists and crushed volcanic rocks are classified a great variety of rocks, ranging in colour from green to grey and almost black, in fissility from the finest lamellation to almost massive forms in which the schistosity is barely evident in the hand specimen, but all definable as fine-grained dark-coloured schistose rocks consisting largely either of hornblende or of its alteration products.
Source: Gutenberg

Get perspective with Kwize: daily news enlightened by great literature