No. 1.] DANA — SOME POINTS IN LITHOLOGY. 45 



which affords, he says, a powder greasy to the touch (the diallage), 

 and also amianthus. He then adds that "in horizontelen Schich- 

 ten in den Gabbro-Bergen um Impruneta findet sich der soge- 

 nannte Granltone, welcher aus weissen Feldspat, der an einigen 

 Stellen Kalchspatartig ist und mit Siiuren brauset, etwas griin- 

 lichtem silberfarbigen wiirflichten Glimmer, und griinlicher Ser- 

 pentin-Erde, besteht: " a description that distinguishes thegabbro 

 from the granitone. Further, he says that some of the granitone 

 consists of the " white feldspar in large parallelopipeds and green 

 gabbro-earth, without the micaceous mineral." 



The word Gabbro, as it is now used (and was so first by von 

 Buch, in 1810), is applied to the granitone, the associate of the 

 Italian gabbro ; but, besides this, to rocks consisting of foliated 

 pyroxene (sometimes called hypersthenite), and cleavable labra- 

 dorite, the idea o^ foliated standing out prominently; and also 

 to an eruptive diabase-like or doleryte like rock, in which the 

 augite happens to be foliated. In this last variety, as the 

 analyses show, there is evidently no foundation whatever for 

 separating the rock from other labradorite-augite eruptive rocks. 

 Granitone is the same as euphotide, a rock distributed at inter- 

 vals along the Alps from Savoy and Isere, in France, through 

 Piedmont, to the valley of the Saas, north of east of Monte Rosa, 

 and the Graubiindten, occurring also in Silesia and on the island 

 of Corsica, and found commonly associated with serpentine. Its 

 chief characteristic is — not its foliated diallajre or smarasdite 

 (either of which is usually a mixture of hornblende and pyroxene), 

 but its consisting largely of the compact jade-like material called 

 saussurite ; for it would be the same rock, essentially, whether 

 the hornblende and pyroxene were distinctly foliated or not ; 

 and, in fact, in part of it the texture is aphanitic, and nothino* 

 foliated is distinguishable. Saussurite has a close relation to 

 some of the feldspars in its constituents, it being essentially a 

 soda-lime- alumina silicate ; and still, as has Ions been recof'nised. 

 it is not a feldspar. This has been rightly sustained by the fact 

 of the high density, which is over 2-9 (2*9 to 3-4) in saussurite, 

 and less than 2'765 in the feldspar group. 



It is further proved by its occurrence occasionally under the 

 crystalline forms of a triclinic feldspar, but with a fine granular 

 or aphanitic structure ; thus bavins:, instead of the cleavage 

 structure belonging to the feldspar, a feature belonging to a 

 pseudomorph. In such cases it was once feldspar ; but some 



