Andkew.— On the Clarendon Phosphate-deposits. 457 



The following fossils were identified in this band, but the 

 specimens collected were very much weathered and mutilated : 

 (1) Serpula, sp. ; (2) Venus obloncja (?), Gray; (3) Dentalium 

 rnantelli, Zittel ; (4) Turbo granosus (?), Lamarck. 



Professor Park* separated the calcareous series at Mill- 

 burn into (a) limestone, (b) glauconitic sandstone. As stated 

 above, however, the glauconitic limestone B affords such a 

 gradual and complete transition between the two that it seems 

 hardly possible to say where the glauconite sand ends and 

 where the limestone begins. Hence I have thought it better 

 to consider the sand as forming the termination of the cal- 

 careous series. 



Glauconite or Chlorite ? — Dr. Maclaurin,f of the Colonial 

 Laboratory, in publishing an analysis of a sample of limestone 

 from this quarry, and apparently from the upper part of band 

 B, describes it as "a whitish limestone dotted with a large 

 number of greenish-black particles (chlorite)." Professor ParkJ 

 had before this described the mineral as glauconite. I isolated 

 a small quantity of the mineral and made a partial analysis 

 of it, as under : — 



Silica .. .. .. .. 49-41 



Water (combined) . . . . . . 10*20 



Not determined . . . . . . 40*39 



100-00 



According to the analyses of different samples given by 

 J. D. Dana,§ the amount of silica in chlorite (penninite) lies 

 between a maximum of 35-31 per cent, and a minimum of 29 - 89 

 per cent. The mineral cannot therefore be chlorite (penninite) ; 

 not is it possible for it to be any other member of the chlorite 

 group of minerals, for stilpnomelane contains the highest per- 

 centage of silica, and that amount never exceeds 45-61 per cent. 

 On the other hand, the published analyses of glauconite show 

 an amount of silica ranging from 46-58 to 52-86 per cent., and 

 in the mineral we are considering we find 49-41 per cent. — well 

 within these limits. Again, paying attention to the amount of 

 combined water in the minerals, we obtain further proof that our 

 mineral is glauconite and not chlorite. In chlorite (penninite) 

 the amount of water ranges between 11 -74 and 16 per cent., 

 both figures being higher than that found with the Millburn 

 mineral. The analysis confirms Professor Park's determination. 



* Professor James Park, Trans. N.Z. Inst. (1902), vol. xxxv, p. 394. 

 f Maclanrin, 36th Ann. Rep. Col. Lab. (N.Z.), 1903, p. 9. 

 % Professor James Park, Trans. N.Z. Inst. (1902), vol. xxxv, p. 394. 

 § J. D. Dana, " System of Mineralogy," pp. 683, 653, 658. 



