1892.] Mineralogy and Petrography. 513 



needles of rutile and six-sided prisms of tourmaline. The colorless 

 mass in which these are imbedded contains plagioclase, orthoclase and 

 quartz. ^The porphyritic crystals in this groundmass are cordierite. 

 They all possess a more or less hexagonal cross section, and the usual 

 optical properties of the mineral. Its inclusions are biotite plates and 

 rutile, and tourmaline crystals like those of the ground mas.-. The 

 composition of the rock is represented by the figures: 



Corresponding to 18% of cordierite, 20% of mica, 30% of orthoclase 

 and 13% of plagioclase. The origin of the rock is unknown. 



Wernerite Rocks occurring at several places in the Pyrenees are 

 stated by Lacroix 1 to be altered feldspathic ,eruptives. The original 

 form of the varieties from Sallix and Ponzac was a hornblende dia- 

 base containing olivine, biotite and sphene. The borders of the feld- 

 spar, which is labradorite, are often fringed by little plates of dipyr. 

 Veinlets of these penetrate the plagioclase until in some cases all the 

 labradorite is replaced by large plates of the scapolite, many of which 

 are of much larger size than the feldspars from which they were 

 formed. They moreover possess a uniform orientation over large areas, 

 so that the structure of the rock passes from the microlitic to the gran- 

 ular. When dynamic agencies have modified it broken pieces of the 

 scapolite are often found. This indicates to the author that in these 

 cases the alteration of the feldspar preceded the crushing. On the 

 other hand, broken pieces of all the other minerals are sometimes 

 found cemented by unbroken dipyr, in which case the formation of 

 the latter mineral was subsequent to the shattering. The alteration is 

 thus a strictly chemical process. The paper closes with a reference to 

 the Norwegian scapolite rocks and their comparison wth those of the 

 Pyrenees. 



Petrographical News.— The phonolites 2 of Montusclat and of 

 Lardeyrols in the Ardennes, in France, contain small crystals and crys- 

 tallites of lavenite, the latter often grouped into forms resembling the 

 skeletons of large crystals. The larger crystals are golden yellow, 

 with a strong pleochroism. 



