280 Professor Hausmann on the Geology of the Apennines. 



acted upon by air and moisture, is broken down and washed 

 away. This most beautiful breccia is known by the name of 

 marble of Seravezza, and is much used for ornamental pur- 

 poses. Our author supposes it to be the variegated stone 

 referred to by Strabo*. 



The celebrated marble of Carrara is considered by Prof. 

 H. as belonging to the transition formation, contrary to the 

 opinion hitherto maintained by geologists. It is connected 

 with and passes into the brecciated limestone and grey 

 waeke, and these rocks alternate more or less with each other. 

 This marble forms high mountains, with steep acclivities, 

 and narrow valleys: the rocks are destitute of vegetation, and 

 distinguished at a great distance by their snowy whiteness. 



The colour of the Carrara marble is injured by exposure, 

 acquiring a brownish tinge probably from a small quantity of 

 iron which it contains. Iron pyrites are found in it, together 

 with calcareous spar and rock crystals. 



Professor Hausmann observes, that when the Carrara 

 marble is cut into long and thin pieces it is flexible like some 

 varieties in North America. 



The next rock described is the Gabbro of Von Buchf; 

 this is one of the most beautiful and remarkable rocks of 

 the secondary formation. Prof. H. observes, that, although 

 from his examination of this rock in the Apennines, he is 

 satisfied that it is not a primitive rock ; yet he would not 

 maintain that Gabbro is in every case a member of the transi- 

 tion formation. Under the term Gabbro he includes serpen- 

 tine, the Gabbro of the Italians, and a rock called in Flo- 

 rence granitone, composed of saussurite and dialloge (Eupho- 

 title of Haiiy). These rocks are shown to be but varieties of 

 the same, often containing asbestos, in which case the hard- 

 ness of the compound is diminished, and the quantity of 

 magnesia in it is increased. Four varieties of Gabbro are de- 

 scribed, viz. 



1. Granular crystalline Gabbro, containing quartz, horn- 

 blende, prehnite, and a substance which has not been ex- 

 amined. This variety passes into jasper. 



2. Porphyritic Gabbro, including the Nero di Prato. The 

 principal part of this variety is serpentine, in which particles 

 of schillerstein are seen. 



3. Spotted Gabbro, principally serpentine with compact 

 globules of saussurite. 



4. Common Gabbro, or serpentine. 



* Gcog. lib. v. 



f Ueber tleri Gabbro, von Leopold Von Buch. Magazin der Gesellsch. 

 naturf. 1810, II. p. 128. 



These 



