382 Transactions. — Geology. 



Madrepore Limestone. — At Keefton a limestone occurs, chiefly composed 

 of large madrepore corals, which if cut and polished would afford a most 

 beautiful ornamental stone. 



Lithographic Limestone. — A stone suitable for most classes of lithographic 

 work has been found in considerable quantities at the Abbey Bocks, West- 

 land, and again at Amuri Bluff ; but at the latter locality it is too much 

 traversed by joints to be of any value. 



Chalk. — Dr. Hector mentions (Trans. N.Z. Inst., vol. ii., p. 178) the 

 occurrence of chalk with flints on Campbell Island, and during 1880 a 

 deposit of chalk, not less than 100 feet thick, was discovered at West 

 Oxford, Canterbury, of which Dr. Hector says (Geol. Bep., 1879-80, p. xviii.) : 

 " The samples of chalk obtained have more perfectly the mineral character 

 and texture of English chalk than any previously discovered in New Zea- 

 land. The rock is pure white, fine-grained, and soft enough to be used for 

 the manufacture of crayons. 



" Its composition as determined by analysis is as follows : — 



Calcic carbonate 



82-26 



Magnesic carbonate . . 



1-84 



Ferric oxide 



traces 



Silica 



.. 15-69 



Water 



0-21 



100-00." 



Stalactites and Stalagmites occur in all the many limestone caves of New 

 Zealand, some of them being of great size and beauty. Of these the caves 

 at Whangarei, Waipu, Collingwood, and Mount Somers are well known for 

 the variety in form and size in which these deposits of lime occur. 



Travertine. — Dr. v. Haast mentions (Jurors' Bep. N.Z. Ex., 1865, 

 p. 256) a deposit of travertine from calcareous waters at the Weka Pass, 

 and it occurs on a small scale in many localities, but no large deposits are 

 known.* 



Limestone occurs very widely distributed throughout New Zealand in all 

 degrees of purity and texture from a marl with 4 or 5 per cent, of carbonate 

 of lime to a limestone which is nearly pure. Hydraulic varieties also exist, 

 and at Mahurangi a deposit of this sort has been worked for some time 

 past. 



Aragonite, Ca C, is by no means of so common occurrence as calcite, but 

 has still been found in a few localities. Dr. Hector mentions it (Jurors' 

 Bep. N.Z. Ex., 1865, p. 266) in cavities in basaltic rocks at Dunediu, and 



* A remarkable deposit of this mineral occurs on the Alfred Eiver, a branch of the 

 Maruia Eiver, in ten-aces which are in the aggregate about 400 feet in height. They are 

 chiefly composed of moss which has been petrified by the calcareous waters, and are now 

 partially clothed by a fresh growth of this moss. 



