ipart 3] MINERALS [N COBAL-LIMESTONES OF BARBADOS. 1<>"> 



of titaniferous iron were also found. The main part of these 

 residua is, however, made up of kaolin and limonite. Quartz is 

 -entirely absent. The largest mineral fragments found measured in 

 millimetres : — 



Felspar. Pyroxene. Glass. 



•20x-10 -07X-07 -13X-12 



The massive corals of the higher reefs, Astrseans, pro- 

 bably Eusmilia, Diploma, and Orbicella, yielded only small 

 proportions of extraneous mineral matters. Prominent among 

 these are small globules of non-striated felspar containing in- 

 numerable crystallites and globulites or vacuoles; a few sharply- 

 angular minute fragments of green and of colourless augite. also 

 of hypersthene ; while sharply-angular conchoidal flakes of both 

 brown and colourless glass are present. Quartz is present in the 

 residua in only very small, practically negligible, proportions. 

 Ferruginous kaolin and limonite are present in smaller proportions 

 in these residua than in those from Mount Misery, the former 

 containing in round figures 66 per cent, of the earthy constituents 

 as compared with 84 per cent, in the latter. The largest mineral 

 fragments found measured in millimetres : — 



Felspar. Pyroxene. Glass. 



■66X-50 -30X-20 -30X-28 



Like the residua from the Mount-Misery calcitized coral, those 

 from the high-level beach-rock contain large proportions of 

 kaolinic and limonitic materials — 76 per cent. — but volcanic debris 

 is more largely in evidence. Small angular fragments of quartz are 

 present, but not in any notable quantity. The largest fragments 

 found are blebs of felspar, some being non-striated, others, however, 

 showing faintly the characteristic stria? of albite, all containing 

 innumerable globulites, vacuoles, and crystallites. 



The bigger fragments generally have a less sharply-angular 

 appearance than have those of the corals; v\hile many of them 

 show well-marked signs of alteration by weathering. The finer 

 constituents are very numerous, and consist largely of colourless, 

 brown, and dark-green glass in small, very sharply-angular con- 

 choidal flakes and splinters, some of the larger pieces having ;i 

 pumiceous structure, and containing numerous minute air-bubbles, 

 while others show inclusions of magnetite. There are also angular 

 and subangular to partly-rounded fragments of green and of 

 colourless augite, and of hypersthene; a few of green-brown horn- 

 blende, very minute angular ones of sanidine, some with microlites 

 and globulites, while some fragments of felspar show faintly the 

 characteristics of plagioclase. Rarely a wisp of dark-brown biotite, 

 and still more rarely a fragment of brown tourmaline, may be 

 seen, while a fair number of fragments of magnetite, of ilmenite, 

 of haematite, and, though seldom, of pyrite are found. The largest 

 mineral fragments found measured in millimetres : — 



Felspar. Pyroxene. Glass. 



•65X-47 -18X-08 -25x-21 



