28 P. T. CLEVE, 



17. Psilomelane (?) very impure, compact, not crystaline, and of black colour is 

 found on the southern coast of S:t Martin in large masses in stratified rocks. 



Composition according to an analysis by Mr. L. J. Westman. 



Si; 31,oi Fe 4,56 Al 5,03 Mn 15,14 Mn 28,16 Ca 5,62 Mg 5,09 H 3,67 Sum. 98,28. 



18. Quartz. Large and fine crystals are found in Puerto Rico (Rio Prieto); small 

 transparent crystals in cavities and fissures in the labrador-porphyry of Culebra. Smaller 

 rock-crystals are also found in fissures in felsitic breccia in S:t Thomas, Tortola etc. In 

 S:t Bartholomew quartz is found in fissures of bard, gray limestone. Quartz crystalized 

 into double pyramids occurs in some varieties of the felsite of S:t Thomas and in the gra- 

 nular granite of Backs Island near S:t Thomas. 



Un crystalized quartz of white colour is very common in veins of different kinds of 

 rocks in the Virgin Islands. 



Ironsilex of red colour is found in S:t Bartholomew and Culebra. Green Quartz oc- 

 curs in fissures in the labrador-porphyry of Culebra. 



Chert is found in large rnasses in S:t Bartholomew, where it has been formed by 

 metamorphic action on volcanic breccias. 



Chalcedony in smaller nests occurs in stratified rocks on the southern coast of S:t 

 Martin. It is also found in S:t Bartholomew enclosed in compact gray limestone. 



Agate of brownish colour is found in Puerto Rico (Caja de Meustos). 



19. Molybdic acid occurs in Molybdena in form of thin layers at Matnayes 

 (Puerto Rico). 



20. Magnetic Iron-ore is observed in Puerto Rico (Gurabo, Ciales), in S:t Martin 

 in small octahedrons, in S:t Bartholomew, Tortola etc. 



Titaniferous Magnetic Iron-ore is an ingredient of the anorthite-diorite of Beef Island 

 near Tortola, where it occurs in small grains or in the form of black loose iron sand, 

 washed down by rains. 



21. Tale is observed in form of small hexagonal leaves in the granular granite of 

 Bucks Island (S:t Thomas). 



22. Wollastonite is found in long whitish gray prisms enclosed in compact limestone, 

 near Anna Bay (S:t John, Virgin Ids.) also in Coopers Island in radiating crystaline masses, 

 accompanied by garnet and pistacite in a strongly metamorphic limestone. 



23. Augite occurs in the diabase or augitic porphyry, in black crystals, in Bucks- 

 Island, near Coki Point and on Hans Lollic near S:t Thomas, also in small greenish-black 

 needles in the labrador-porphyry of Culebra. 



24. Homblend is very common in the rocks of the Virgin-Islands. Large crystaline 

 masses are found near S:ta Cruz in the small Green Cay, and in the anorthite diorite of 

 Beef Island near Tortola, also in Puerto Rico (Rio de la platå). Small black needles of 

 hornblend occur in the trachyte of Saba and in the syenite-porphyry of S:t Bartholomew. 

 — It is a constituent mineral in the diorites of the Virgin-Islands. 



25. Chrysocolla is found in Puerto Rico (Rico Blanco), in S:t Martin, and in Coo- 

 pers Island. 



26. Resanite. By this name I propose to call a trisilicate of copper and iron with 

 water found in Puerto Rico (Luquillo) by Don Pedro Resano. It occurs in olive green, 



