ON THE GEOLOGY OF THE NOETHEASTERN WEST-INDIA ISLANDS. 27 



Having now concluded the report on the geology of the north eastern West-India 

 islands, visited by me, I will in the following enumerate and describe the minerals and 

 rocks found in those islands. 



Y. Minerals and Rocks found in the Northeastern West-India 



Islands*). 



1. Sulphur of volcanic origin is found in the volcanic islands of Saba, Nevis and S:t 

 Kitts. It is formed by oxidation of sulphuretted hydrogen and commonly accompanied by 

 gypsum and alum-stone etc. In Puerto Rico sulphur is found at Mameyes (Sierra Luquillo) 

 It seems here to be derived from the decomposition of pyrite. 



2. Gold is found in loose pieces in the rivers of Sierra Luquillo and Corazal in 

 the island of Puerto Rico. 



3. Mercury in Puerto Rico (Rio grande, Luquillo). 



4. Copper. Virgin Gorda. The metal is dendritic. It occurs in veins of white 

 quartz, traversing diorite, and is accompanied by several copper minerals as well as by 

 molybdena. 



5. Pyrite is very common in most of the islands. Large crystals are found on 

 Puerto Rico (Sierra Luquillo) on S:t Bartholomew (cubes enclosed in volcanic tufas of 

 eocene date, near L'anse publique and near the mines) and on Virgin Gorda in the copper- 

 mines, crystalized in pentagonal dodecahedrons. 



6. Blend. S:t Bartholomew in the mines; very scarce. 



7. Galena is found in S:t Bartholomew, sometimes crystalized in cubes; also in 

 Puerto Rico (Sabana grande, camino de lauro). 



8. Molybdena occurs in Virgin Gorda and in Puerto Rico (Mameyes). 



9. Magnetic pyrite is observed at Rio blanco on Puerto Rico. 



10. Chalco-pyrite is found in S:t Bartholomew in smaller pieces, in Tortola, and also 

 in Virgin Gorda. 



11. Gray Copper-ore. Smaller pieces are found in S:t Bartholomew and in Virgin 

 Gorda. 



12. Red Copper-ore occurs in Puerto Rico (Corozal) and in Virgin Gorda. 



13. Black Oxide of Copper (Kupferschwärtze) very scarce in S:t Bartholomew and 

 in Virgin Gorda. 



14. Specular Iron is found in several places on Puerto Rico (Rio Cugull) in Tor- 

 tola in veins of quartz in the eastern part of the island; in S:t Martin accompanied by 

 manganese in stratified rocks on the southern coast; in S:t Bartholomew near the mines in 

 small scales. 



15. Manganite Puerto Rico (Corozal) not found in crystaline form. 



16. Limonite is found in S:t Bartholomew in stalactitic form. In S:t Martin in 

 colloid state and also observed in Puerto Rico (Rio blanco). 



') For the acount of tlie minerals of Porto Rico I am entirely indebted to Don Pedro liesano of San Juan. 



