274 Gustav Rose on Greenstone and [Oct. 



grains; and when the hornblende predominates, becomes 

 often very fine granular, and appears to pass into compact 

 masses. 



In diorite where the albite prevails, the hornblende often 

 lies in single crystals and grains in the granular albite 

 (Frolowsche Mine, at Bogoslowsk, in Ural), and likewise 

 in diorite where the hornblende predominates ; the albite 

 occurs in individual crystals and grains in the granular 

 hornblende (Turdojak, at Miask, in Ural.) It sometimes 

 happens, also, that large crystals of hornblende occur in a 

 porphyritic manner, in a finely granular mixture of albite 

 and hornblende, (rolled masses in the neighbourhood of 

 Berlin.) 



The different grains of one and the same constituent, as 

 well as of different ingredients, are difficult of separation. 



A portion of diorite, from Alapajeusk, in Ural, consis'ting 

 of albite and hornblende, the first predominating, weighed 

 32*0332 grammes, (495i grs.) and possessed a density of 

 2-792. 



The same variety, when heated in a platinum crucible, 

 melted into a greenish black, and in thin portions, into a 

 greenish white transparent glass. A variety, very rich in 

 hornblende, from Nichne-Isetsk, near Katharinenburg, in 

 Ural, melted, in a charcoal crucible, into a white mass, 

 translucent on the edges, possessing a fine splintery frac- 

 ture. At the bottom, an iron regulus was formed, on the 

 sides of which were seated other small iron reguli. The 

 large portion contained small crystals, and pieces of tita- 

 nium, which were easily recognized, by their copper-red 

 colour, and their remaining undissolved in the solution of 

 iron in nitric acid. Hence, we see that titanic acid, when it 

 occurs in minute quantities in diorite, is probably an acci- 

 dental constituent of the albite and hornblende, as happens 

 with mica. It does not exist to an appreciable amount in 

 the diorite of Mapajewsk.* 



The diorite occurs under the greenstone of Ural, pretty 



* G. Hose considers that to melt titaniate of iron in a charcoal crucible is an 

 excellent method of separating the iron from the titanium, as titanium is insoluble 

 in aqua regia. Titanic acid, when fused with bases, forms crystalline products. 

 Several titanic acid combinations which occur in nature, crystallized, appear to 

 assume a different form by melting. Yellow titanite forms a black mass, consisting 

 of rhombic dodecahedrons. Brovsoi titanite, from Ilmengebirge, forms black, 

 undefined crystals. 



