189 6.] Petrography. 45 



limestone whose relations to the blue limestone of the same region have 

 been so much discussed. The granite contains black hornblende, a 

 little biotite, and so much plagioclase that some phases of it might well 

 be called aquartzdiorite. Allanite and fluorite are also present in the 

 rock, the former often quite abundantly. As the granite approaches 

 the limestone it becomes more basic. Malacolite, scapelite and sphene 

 are developed in it in such quantity, that immediately upon the con- 

 tact the normal components of the granites are completely replaced. 

 On the limestone side of the contact the rock becomes charged with 

 silicates, the most abundant of which are hornblende, phlogopite, light 

 green pyroxenes, sphene, spinel, chondrocyte, vesuvianite, etc. The 

 contact effects are similar in character to those between plutonic rocks 

 and limestones elsewhere. The blue and the white limestones are re- 

 garded as the same rock, the latter variety being the metamorphosed 

 phase. 6 



An Augengneiss from the Zillerthal.— The change of a gran- 

 ite porphyry into augengneiss is the subject of a recent article by 

 Fiitterer. 7 The rocks are from the Zil lerthal in the Alps. The gneisses 

 are crushed and shattered by dynamic forces until most of the evidences 

 of their origin have disappeared. The original phenocrysts have been 

 broken and have suffered trituration on their edges, while new feldspar, 

 quartz, malacolite and other minerals have been formed in abundance. 

 The groundmass of the gneiss is a mosaic whose structure is partially 

 clastic through the fracture of the original components and partially crys- 

 talline through the production of new substances. The author's study 

 is critical, and, though he treats the described rocks from no new point 

 of view, he discusses them with great thoroughness, calling attention at 

 the same time to the important diagnostic features of dynamically met- 

 amorphosed rocks. 



Petrographical News. — Ransome 8 has discovered a new mineral, 

 constituting an important component of a schist occurring in the 

 Tiburon Peninsula, Marin Co., Cal. The other components of the 

 schist are pale epidote, actinolite, glaucophane and red garnets. The 

 new mineral, lawsonite, is orthorhombic with an axial ratio .6652:1 : 

 .7385, a hardness of 8 and a density 3.084. The axial angle is 2V= 

 84° 6' for sodium light. Its symbol is H 4 Ca Al 2 Si 2 O 10 - 



•J. F. Kemp and Arthur Hollick: X. Y. Acad. Sci., VII, p. 638. 



7 Xeue> Jahrb. f. Min., etc, B.B. IX, p. 509. 



8 Bull. Geol. Soc. Araer., Vol. 1, p. 301. 



