54 Professor T. G. Bonney — On Rocks from Ararat. 



amblystegite, while in others the extinction angle varies, being once 

 or twice large enough for augite. 



"Below the summit of Great Ararat (B)." Twenty-eight rock 

 fragments, some of them very small, were collected just below the 

 summit' of Great Ararat, at about 16,700 feet. They vary much in 

 colour and aspect, but probably include only three or four varieties. 



One group (B, a) appears to be represented in its freshest con- 

 dition by a dark-grey rock resembling that already described, and 

 the microscope shows no great difference. The glassy base is 

 a little more ferrite-staiued and has fewer distinct transparent 

 microliths ; the plagioclase felspars have fewer and smaller glass 

 enclosures ; the pyroxenes are similar, one or two being certainly 

 augite. 



A second group (B, h, 2) is represented in its freshest state by 

 a slightly darker, more porous, more porphyritio rock. A slice of 

 it shows a larger amount of glass than the others, this being 

 of a rich brown colour with granules of opacite and a fair number 

 of transparent microliths. In it we find grains of iron-oxide 

 (hematite in part) ; plagioclase felspars, generally idiomorphic, 

 occasionally with rather abundant glass enclosures in the larger 

 specimens (probably from partial melting), and a light - brownish 

 pyroxene, some crystals of it certainly augite, perhaps one or two 

 amblystegite. 



Three specimens (B, 6, 1) of a blackish glassy material studded 

 with small crystals of white felspar. The specific gravity of one 

 specimen is 2-483.'^ A slice cut from one of the specimens shows 

 a glass which exhibits a fluxional structure and is present in larger 

 amount than in any of the other rocks. It is generally brown, but 

 with almost colourless streaks, is studded with microliths, both 

 minute belonites and small prisms apparently of felspar, and is 

 slightly spotted with granules of iron-oxide. In this base are 

 crystals, sharp-edged, broken, or rounded, of plagioclase felspar, 

 magnetite, or hematite, hornblende and amblystegite. Glass 

 enclosures in the felspar are small in size and variable in amount, 

 in several cases developed mostly in the exterior zone. The rock is 

 a pitchstone (andesite). 



A number of light - coloured fragments (B, 6) varying from 

 yellowish-grey to almost white, the differences probably being due 

 to the amount of decomposition. A specimen sliced shows the rock 

 to be less well preserved than the others, but its differences are only 

 varietal. It also contains amblj'stegite. 



The description of Herr Abich's specimen, said to come from the 

 summit of Great Ararat (on which no rock was exposed when 

 Mr. Lynch reached it), agrees so closely with that given above 

 under B, 6, 1, that I have little doubt the rocks are substantially 

 identical. His specimen contains a rhombic pyroxene which 

 Dr. Becke names bronzite, but which I think would now be regarded 



1 The highest rock visible at the time of Mr. Lynch's visit. 



2 Determined by "Walker's balance. 



