ART. 18 MINERALS OF ITALIAN MOUNTAIN" CEOSS AND SHANNON 37 



mal or on a less perfect cleava<ie at right angles to this. This shows 

 rather high birefringence and a considerable range in refractive 

 indices, y varying from 1.495 to 1.500. (No. 84578.) This stilbite in- 

 closes occasional small plates of specular hematite. It appears to 

 have grown outward from the walls of open cavities, leaving some 

 small unfilled centers which were later occupied by finely fibrous 

 radiating white scolecite. Another specimen (No. 84580) from Tay- 

 lor Peak shows very similar brownish stilbite and dense scolecite, 

 but here the first lining of the cavity consists of large crystals of 

 the sahlite variety of pyroxene. The best specimens of stilbite are 

 from Taylor Peak, and consist of sheaves of divergent imperfect 

 crystals of stilbite up to 6 or 7 mm. long, resting on much-altered dull 

 and rusty cliopside rock. These grow outward from radiations of 

 coarse pearly needles of the zeolite here referred to scolecite, the 

 stilbite in this case being distinctly younger than the scolecite, 

 although elsewhere clearly older. Another specimen shows abun- 

 dant stilbite in poorly developed crystals tending to form sheaves 

 2 by 1 mm. in size in calcite, which has exposed them by partly leach- 

 ing away. (Nos. 84581, 84582.) 



A sample of stilbite from the Italian Mountain collection was 

 analyyjed by Eakins with the following results : 



Analyfiis of stilbite 



SiO:- 57. 75 



AI2O3 16. 64 



CaO 8. 58 



NajO Trace. 



H.0 17. 17 



Total 100. 14 



HEULANDITE 



Heulandite occasionally makes up a fairly conspicuous constitu- 

 ent of a specimen and in many other cases occurs in small amount. 

 One of the most showy specimens of heulandite in the collection 

 (No. 84575) shows this zeolite occurring along a crack in massive 

 coarse granular garnet rock. The heulandite forms large crystalline 

 masses to 4 cm. long showing j^erfect cleavage in one direction with 

 pearly luster on the cleavage face. Interspersed with these larger 

 masses are also small, 1-2 mm., clear glassy perfectly developed 

 crystals scattered sparsely over the rock or aggregated into small 

 clusters. These have the habit of the " beaumontite " of Jones 

 Falls, Maryland. The locality for this specimen is Bidwell Range, 

 Gunnison County. Another specimen of heulandite having the same 



