ABT. 18 MIlSrERALS OF ITALIAN" MOUNTAIlSr CROSS AND SHANNON" 33 



widely distributed zeolitic mineral of the Italian Mountain locality. 

 It occurs not only associated with the other zeolites, chabazite and 

 stilbite as a late deposit in cavities but is also common in minute cavi- 

 ties in the dense garnet hornfels which forms the matrix of the best 

 vesuvianite specimens and replaces, to a greater or less extent, the 

 mizzonite variety of scapolite in almost all specimens of the latter 

 mineral. 



In the hornfels which, in its cavities, bears the fine vesuvianite 

 crystals, tiny vugs in massive pale-brown garnet which are lined with 

 minute grossularite crystals are partly filled with a white fibrous zeo- 

 lite which ranges from translucent compact radial or divergent fibrous 



14 15 



Figs. 14-15. — Cry.st.\ls of Quart* 



tough material to loosel}' grouped separable fibers. The former con- 

 tinue out and terminate in the latter (No. 84553). The free fibers 

 have negative elongation and a small inclined extinction, X A c = lQ°. 

 The mineral is apparently optically negative, the birefringence is 

 low, and the mean index of refraction is about 1.510. These prop- 

 erties identify the mineral as scolecite. The compact-fibrous material 

 has the same index, birefringence, and elongation and, although the 

 inclined extinction can not be seen, owing to the fine fibrous char- 

 acter, it is doubtless the same mineral. Another specimen of garnet- 

 diopside hornfels which was examined contains abundant minute 

 pores filled with a soft radial-fibrous white zeolite of the same prop- 



