AET. IS :\IIXEEALS OF ITALLIN MOUXTAIX — CEOSS AND SHANNON 1 1 



position is 1.747. Several specimens from the same lot were 

 examined optically. One specimen of small transparent very pale 

 brownish crystals overlain b}^ chabazite and a little scolecite was 

 found to be colorless and transparent and completely isotropic with 

 a homogeneous index of 1.745. Another of transparent pale amber 

 crystals was 1.752. Nearly, colorless crystals 5 mm. in diameter had 

 an index of 1.746. An aggregate of fairly large crj^stals of a brown 

 color, translucent in the hand specimen, showed distinct birefringence, 

 and, although the index of the bulk of the material was about 1.75, 

 the crystals are evidently zoned and vary in index from 1.752 to 

 about 1.780. Another specimen showing very large crj^stals — ^up to 4 

 cm. in diameter — appears slightly zoned in color in the hand speci- 

 men and ranges in index from 1.753 to 1.756, Most of the nearly 

 transparent crystals seem to approximate closely the calculated 

 refractive index. 



This brown grossularite occurs not only as the crystals described 

 above but also makes up large masses of dense garnet rock, some- 

 times almost pure but usually containing considerable amounts of 

 diopside, even when no green color due to the diopside can be 

 detected. Such garnet-diopside hornfels forms the matrix of the 

 crystallized grossularite specimens and also of the numerous speci- 

 mens which bear vesuvianite in the cavities. One dense lustreless 

 hornfels of pale brown color, the cavities of which were lined with 

 nearly colorless grossularite, was found to consist of approximately 

 equal parts of fine-grained colorless diopside and colorless isotropic 

 garnet with an index of refraction of 1.745 (No. 84553). The matrix 

 of one of the best specimens of vesuvianite (No. 84548), a tyx^ical 

 hornfels of this lot of specimens, likewise shows a large proportion 

 of colorless isotropic garnet the index of which ranges from 1.745 to 

 1.748. 



A second lot of garnet decidedly different from the last (No. 

 84556) is labeled as from North Italian ISIountain and contains 10 

 specimens. This consists of brilliant sulphur-yellow to greenish 

 sulphur-yellow crystals of perfect dodecahedral form averaging only 

 about 3 mm. in diameter. These little garnet crystals appear dis- 

 seminated through coarse granular calcite, sometimes sparsely and 

 sometimes so thickl}' as to make up solid masses of granular garnet 

 rock. Usually the garnet is alone, but in a few specimens it is 

 accompanied by vesuvianite in perfect little embedded crystals of a 

 brown color. This garnet was also analyzed by Eakins, the results 

 being given, with ratios, below. 



