492 Heivett and Sliannon — Orientite, a new 



which pitches to the west. The southern limit of the 

 trough is the igneous complex of the Sierra Maestra ; the 

 northern limit is a group of low ranges near the north 

 coast, largely made up of serpentine. The trough com- 

 prises a great thickness, possibly 8,000 to 10,000 feet, of 

 bedded volcanic breccias, and tuffs with andesite and 

 latite flows, and limestone. On the southern limb of the 

 trough tuffs, breccias and flows constitute more than 95 

 per cent of the lower 2,000 or 3,000 feet but the proportion 

 of limestone is larger than that of the igneous rocks in the 

 upper 2,000 feet or more. The lower course of the Cauto 

 River approximately follows the trough. The manganese 

 deposits occur over a wide stratigraphic range in the 

 middle part of the section, to which an upper Eocene age 

 has been tentatively assigned. 



The minerals of the manganese deposits of Cuba, in 

 order of abundance, are psilomelane, both hard and soft 

 varieties, manganite, pyrolusite, wad, neotocite and 

 orientite. 



The accessory minerals include "bayate" or ferrugi- 

 nous jasper, glauconite ( ?), barite, quartz, calcite and 

 several zeolites. Although a few bodies of manganese 

 oxides occur in limestone or the clay resulting from its 

 decay, most of them replace fine tuff or volcanic ash. 

 They assume many forms, dependent upon local structural 

 features. 



Orientite was first found in a group of deposits on the 

 Costa, Manuel and Vicente claims, 6 miles south of Buey- 

 cito and 20 miles southwest of Bayamo. Later it was 

 found in material from the Santa Eosa prospect, near 

 Banes, north of Antilla. An amorphous hydrous silicate 

 of manganese which is probably neotocite, was found in 

 material from the Abundancia mine at Manganeso. 

 Material encountered in several other deposits (Isabelita, 

 Ponupo, Llave) indicates that neotocite, and possibly 

 orientite, was once present but has been destroyed by 

 weathering. Neither mineral was definitely recognized, 

 however, in the Jutinicum, Dos Bocas and Baire districts, 

 which were also examined. 



Orientite was first recognized as minute reddish-brown 

 crystals that lined drusy cavities in Open Cut No. 8 on the 

 Costa claim, and similar material was later found at many 

 other open cuts on the Costa, Manuel and Vicente claims. 

 Later, when thin sections of material from other openings 

 were studied, it was found that orientite was widespread, 



