part 3] MINERALS IN" C0BAL-LIMEST01TKS OK BARBADOS. 



163 



In order to ascertain the composition, nature, and origin of the 

 extraneous mineral or acid-insoluhle constituents of the coral- 

 limestone, examinations, both chemical and microscopical, have 

 been made of the residua obtained by the mode described, with the 



following results : — 



Ultimate Chemical Composition'. 



2. 



Quartz with cbalcedonic SiOg ... — 



SiOs (organic opaline) 2 - 07 



Combined Si(>.> 41-08 



Combined IU) 11-59 



Al.O, 27-17 



I-V.O ;i 13-26 



FeO -88 



MnO — 



TiOo 1-75 



CaO -15 



MgO 1*44 



K-O -27 



NaoO -39 



P 2 6 -o2 



Totals 100-67 



•06 



1-65 



35-58 



11-87 



27-32 



1449 



221 



•37 



2-58 



•21 



1-47 



•59 



1-45 



•01 



1. 



L2 

 19 



11 

 37 



03 



64 I 



79 



-I 



00 



70 



83 



l:; 



35 



01 



1306 

 6*54 



36'36 

 4-82 



1668 



1095 



2-59 



1-98 

 2-60 

 1-21 



109 



2-70 



•02 



20-11 

 4*07 



32 ^2 

 8-13 



21-38 

 615 

 2-27 



1-52 



•20 

 1*39 

 •92 

 •90 

 ■01 



99-89 loo-04 i 100-60 



99-87 



1. Mount-Misery coral ; 2. High-bvel corals ; 3. High-level beach-rock ; 

 1. Low -level corals ; 5. Low-level beach-rock. 



During the analyses the constituents of the residua which are 

 unattacked by hot sulphuric acid were separated from those con- 

 stituents which were thereby rendered soluble in dilute acids, or. 

 in the case of silica, in a warm dilute alkaline solution. The con- 

 stituents of the acid-resisting fractions are as follows :— 



Percentage Composition of tuk Minerals and Glass not 

 decomposable by hot sulphuric acid. 





1. 



2. 



3. 



*■ 



5. 



Quartz with cbalcedonic Si0 2 . 



'. 72- 1 



e-G 



nil 

 507 

 nil 

 9-61 

 4*06 

 2-03 

 "51 



105 

 71-57 



n-ia 

 nil 

 7*56 

 nil 

 •84 

 1-68 

 1-05 

 2-10 



39-77 



43 63 



8-68 



nil 



IJ33 

 •58 

 •39 



116 

 •78 

 •39 



33-26 

 W30 



1 1 •( 15 

 2 55 

 1*63 

 ■is 

 3-70 

 1-04 

 1-35 

 512 



64 I .» 



2261 



668 



nil 



1-46 



19 



■64 



111 



■76 



11 



A1 2 3 



K. ..<)■, 



FeO 



Tin., 



CaO 



MgO 



K.,<> 



Na.,<) 



Totals 



100-01 





100-01 



10 1-18 





| 









Some, if not all, of the ' quartz ' in the residua from the rocks of 

 the higher levels is secondary cbalcedonic silica, while part, if not 



