﻿374 MR. FEEDEEIC P. MENNELL ON THE [Aug. I9IO r 



Mine was made by Mr. W. C. Hancock. An analysis of Kimberley 

 pyrope is quoted for comparison. 



I. I A. 



Colossus Mine (Bhodesia). Kimber lei/ (Cape Colony). 



Si0 2 40-43 41-34 



Fe Q 3 4-94 — 



A1 2 3 19-13 22-75 



Cr.,0 3 2-12 2-96 



FeO 866 1212 



MnO 0-12 036 



CaO 4-44 5-17 



MgO 20-33 16-20 



Totals 100-17 100-90 



Specific gravity = 3'72 



The Rhodesian garnet is therefore a more typical pyrope than 

 that from the Kimberley pipe, although the general similarity in 

 constitution is very close. It is naturally interesting to compare 

 the composition of the garnets in the eclogite fragments with the 

 pyrope ; and as I am not aware that this has hitherto been done, I 

 caused the following analyses to be made by Mr. Hancock, of 

 material carefully picked out in the Mineralogical Laboratory at 

 Cambridge from fragments of eclogites collected by myself. 

 Analysis II shows the composition of the garnet of specimen A 

 described above (p. 373), while Analysis III represents a more 

 reddish garnet from some much smaller eclogite- fragments among 

 the concentrates obtained in washing. It may be stated that, 

 despite very exceptional opportunities, I have never succeeded in 

 obtaining any eclogite showing garnets of the deep red colour of 

 those common in an isolated state in the matrix itself, nor have I 

 seen them in any of the numerous eclogite-fragments that I have 

 examined from the Kimberley Mines. 



Analyses of garnets from eclogite. 



II. III. 



Si0 2 40-44 39-87 



Fe 2 3 6-51 4-95 



Al o 3 23-69 21-47 



OjOa 032 0-26 



FeO 1138 8-10 



MnO 0-60 0-23 



CaO 986 12-32 



MgO 7-72 1289 



Totals 100-52 100-09 



Specific gravities = 3 -75 3'64 



It is not easy to pigeon-hole the above among the ordinary 

 varieties of garnet, but it is evident that they differ markedly from 

 the pyrope of the Colossus Mine. 



Before passing from this subject, reference may be made to the 

 composition of the augite, which, together with garnet and ilmenite r 



