Hydrous Silicate of Manganese and Calcium. 



497 



the analyses which follow show that although it is a 

 hydrous ^ silicate of manganese, it is deficient in lime, if 

 indeed lime is a part of it. Its relation to the oxides, 

 bayate, and orientite, indicates that it was deposited 

 essentially contemporaneously with orientite. 



Zeolites are present at many openings on the Costa, 

 Manuel, and Vicente claims near Bueycito, but are not 

 conspicuous in several other localities that were exam- 

 ined. The commonest zeolite near Bueycito is stilbite 

 which generally fills veinlets that cut the mineralized 

 tuffs. Analcite^^in crystals up to 1 cm. in diameter, chaba- 

 zite in rhombohedrons up to 5 mm. in diameter and lau- 

 montite in bundles of lath-shaped crystals, cover drusy 

 cavities at a number of localities. These four zeolites 

 uniformly appear to be deposited later than orientite and 

 the manganese oxides. 



Quartz occurs in druses, here and there as doubly ter- 

 minated dark gray crystals. The color is due to included 

 minute grains of manganese oxide and here, at least, 

 appears to have been deposited contemporaneous with and 

 later than the oxides. Its relation to the zeolites has not 

 been determined. On the other hand, "bayate," a 

 brownish jasper or chalcedony which is made up of minute 

 spherulites and is almost universally abundant near every 

 manganese deposit in Cuba, appears to be earlier than or 

 contemporaneous with the manganese oxides.' A clear 

 limpid amorphous mineral that is probably opal is present 

 in some thin sections. It appears to have been deposited 

 after the oxides of manganese and orientite, but its rela- 

 tion to calcite and the zeolites is not clear. 



Barite occurs in the deposits as radiating aggregates 

 of thin tabular crystals intimately associated with orien- 

 tite, and as clusters of tabular crystals in druses in man- 

 ganese oxides. Most of it appears to have been deposited 

 contemporaneously with orientite. 



Glauconite (f) is intimately associated with bayate in 

 most deposits. It forms thin fibrous green films on the 

 borders of the bayate masses generally adjacent to the 

 unaltered tuff's and most remote from the bodies of man- 

 ganese oxide and orientite. The identification of the 

 mineral near Bueycito is based wholly on the index of 

 refraction (1.61) and the birefringence. 



Materials having the same properties and associations 

 was collected by Burchard in several districts in Cuba.'^ 



' Burchard, E. F., loc. cit., p. 58-60. 

 ^Eurchard, E. F., loc. cit., p. 89. 



