ON THE GEOLOGY OF THE NORTH-EASTERN WEST-INDIA ISLANDS. 31 



39. Carbonate of Iron occurs in fissures of the felsite-conglomerate of S:t Thomas and 

 in the diorite of Virgin Gorda, Coopers Island etc. 



40. Carbonate of Lead is found in the lead-mines of S:t Bartholomew in small white 

 or reddish-white crystals. 



41. Malachite occurs in Puerto Rico (Rio Blanco) Virgin Gorda, and S:t Bartho- 

 lomew. 



42. Blue carbonate of Copper is found in small iine crystals and also uncrystalized 

 in the lead-mines of S:t Bartholomew. 



43. Titanite (Sphe n) is very rare and found in almost microscopical yellow crystals 

 in the diorite of Browns Bay (S:t John), and in quartz-veins in the same island. 



44. Barytes (Heavy Spar) occurs in large white masses in the lead-mines of S:t 

 Bartholomew. 



45. Celestirie is found in small iine transparent and colourless crystals in the in- 

 teriör of fossil shells at Brimstone Hill (S:t Kitts). The crystals have 'the form 



r 00 • r GO • CO L • 



46. Anglesite is found in S:t Bartholomew in the form of grayish white, scarcely 

 crystaline, masses. It has evidently been originated by oxydation of galena. 



47. Double sulphate of sodium and alumina (Natronalaun) is found in S:t Bartho- 

 lomew in the walls of a cave near the sea, not far from Grand fond. It occurs here to- 

 gether with Gypsum and Bartholomite. The mineral is produced by alteration of pyrites, 

 imbedded in rocks containing alumina and continually irrigated by spray from the sea. 

 The mineral occurs in small snow-white crystaline masses of thin scales. It is very so- 

 luble in water. 



According to an analysis by P. T. Cleve it contains: 



S 45,64; Al 14,50; Na 9,25; H 31,11 Sum. 100,50. 



From the formula Na S -\- Al S 3 -f- 1 2 H one may calculate: 



S 45,68; Al 14,63; Na 8,85. H 30,84 Sum. 100,oo. 



48. Bartholomite, a new compound of basic sulphate of iron and sulphate of sodium. 

 It occurs together with the preceding mineral in S:t Bartholomew and is also produced 

 by alteration of pyrites. It forms yellow nodules composed of small needles. 



The analysis of this mineral by P. T. Cleve has given: 



Na Cl 2,88; Insoluble matter 3,56; S 44,75; Fe 22,71; Na 17,08; H 8,08; Mg 0,63 Sum. 99,69. 

 — If we subtract from the result 2,88 Na Cl; 3,87 Mg S — |— 7 aq; 3,56 insoluble matter, and 

 calculate the rest in 100 parts we get S 48,66; Fe 25,41; Na 19,11; H 6,82 Sum. 100,00. 



The formula 2 Na S+Fe S, + 2 H requires S 50,00 Fe 25,00 Na 19,38; H 5,62. 

 Sum. 100. 



The mineral is thus closely related to Botryogen. 



49. Gipsum is found in very different kinds of rocks. In volcanic and trachytic 

 rocks it occurs in several islands as Saba, S:t Eustatius etc. In clay or marl it is found 

 in Anguilla, and also in S:t Bartholomew. 



50. Sombrerite (Collophane of Sandberger) 3 Ca O, P0 5 -f- HO. Phosphate of lime 

 is^found in the small island of Sotnbrero, where it occurs in many different forms. Soine 



