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The Pamphlet Collection of Sir Robert Stout: Volume 64

Rich Limes

Rich Limes.

The English and foreign types given in Table I. comprise eight examples that range in purity from statuary marble, a pure carbonate of lime, to the carboniferous limestone of Whiteford in Wales, that has ten per cent, of impurities. It will be observed that ordinary white chalk approaches nest to marble in purity, it only contains ½ per cent, of foreign ingredients.

Analyses are given of fifteen Otago limestones that furnish rich limes, which shall now be considered seriatim.

No. 9 is a white; compact, crystalline stone from Southland, locality unknown, probably Winton. Its constituents are 98.80 per cent, of carbonate of lime, and 1.20 per cent, of soluble silica. It is thus entirely worthless as a cementing material.

No. 10. A compact crystalline stone of faint yellow colour from Winton evidently closely allied in all its essential properties to the preceding one and equally deficient in cementitious qualities. I believe that these two specimens are fair samples of the stone in the vicinity of Lime Hills, Winton, of which there are about 1000 acres.

No. 11. Fossiliferous, compact, and very hard stone of a dirty yellow colour, from Kakanui. This specimen was analyzed by Professor Black for Mr. Cairns. It contains 98 per cent, of carbonate of lime and magnesia and 1½ per cent of sand, consequently must be placed in the same category as the Southland limes. The stone is burned extensively for building page 115 purposes, so I am sure the houses in which it is used cannot be very dry.

No. 12. Yellow fossiliferous stone from the Oamaru district, the precise locality unknown. It is referred to by Dr. Hector as a stone largely employed by Mr. Hutcheson for burning into lime. From the analysis and description given it must be closely allied to the preceding specimen.

No. 13. Soft fossiliferous stone from the eastern side of Waihola Gorge, white in colour, granular in texture, and very absorbent. This is not so abundant nor so much used as the hard variety No. 16.

No. 14. Yellow lithographic stone from the Oamaru district. It has all the external appearances of a lithographic stone, but does not exist in large quantities; it is found associated in the same rocks with No. 12.

No. 15. Grey and yellow travertine limestone of a porous texture from the Dunstan Gorge. This stone, which is sometimes called calcareous spar, is formed by the deposition of lime held in solution in the water of streams and springs. The water acquires the lime in flowing over or through rocks containing this mineral, and it is deposited in concretionary masses on the banks. Travertine is found in the small creeks that flow into the Clutha and Kawarau rivers between Clyde and the Shotover. This stone was first burned for lime in 1864, when it was used in the masonry of the Gentle Annie Bridge.

No. 16. White, compact, and very hard stone from Waihola. This is the stone from which the well-known Waihola lime is produced. It exists in large quantities in available positions on both sides of the gorge through which the railway runs. The rock is very much shattered and dislocated, few of the horizontal joints being more than six inches apart. This facilitates quarrying and breaking, and to some extent balances the excessive hardness, which otherwise would be a great barrier to cheap working. I regret that the Waihola limestone cannot be pronounced good, as, from its favourable situation, it would be an immense boon to Dunedin and the surrounding districts. The limestone contains 94½ per cent, of carbonate of lime, which is decidedly too rich for building in a damp situation, or where strength is required. This, and analysis No. 13, by Dr. Hector, are copied from an old advertisement of Dr. Croft's; they refer to specimens taken from the eastern side of the gorge, but I believe the stone now used, on the western side, is equally pure with No. 16. Indeed, it was lately stated in the papers that it contained 98 per cent, of carbonate of lime, which, if correct, makes the matter still worse.

No. 17. Grey granular stone from Oamaru, found in the same locality as Nos. 12 and 14. It contains 2½ per cent. less carbonate of lime than the former, and is therefore so much letter in quality.

No. 18. Bluish-grey compact stone from Dowling Bay. This is a page 116 sample from the top scam. Although a rich lime it contains small quantities of all the ingredients that give hydraulicity with little sand, consequently it will make fair mortar for ordinary work in a dry situation. It forms one of five beds of limestone that occur at Dowling Bay, Lower Harbour, the particulars of which will be given further on.

No. 19. Fawn colored, incoherent, and absorbent stone from Aparima, in Southland. It contains 92 per cent, of carbonate of lime, and 5½ per cent, of insoluble matter, the precise nature of which is not stated. As the chances are that this is not all sand, we may pronounce the sample a good lime of its class.

No. 20. Compact grey stone from Fews Creek, Lake Wakatipu. According to the analysis, this sample contains 4½ per cent, of insoluble matter not detailed out, but Dr. Hector says that this consists of black sand, iron pyrites, and bituminous matter, in which case the quantity of sand must be inappreciable. The stone will yield lime suitable for ordinary building purposes in the dry atmosphere of the Lake district in which it occurs. Another specimen of stone from this locality was analyzed by Professor Black, with the results given in item No. 16, Table II. It contains 12½ per cent, of sand, so I had no hesitation in putting it in the class of poor limes. There is nothing strange in the discrepancy between the two analyses. They may both be correct, although the samples had been collected within a few feet of each other. Impure limestone deposits all over the world have the same character of irregularity in composition between the various strata. The difference may therefore be accepted as a favourable indication of the quality of the Wakatipu limestone. In all probability the intermediate beds will produce strong hydraulic limes. In his "Geology of Otago," Captain Hutton estimates the thickness of the calcareous deposits in the vicinity of Fews Creek at 600 feet, and reports the existence of similar rock at Afton Burn, on the west side of the lake, and at Stoney Creek, on the Upper Shotover.

No. 21. Bluish compact stone from the Horse Range. This stone belongs to the higher class of crystalline limestones, such as partake of the character of marbles; indeed, it merges into true marble in many places. The deposit occupies a large area of the western side of the range, near Palmerston, in accessible situations for working. With proper treatment this stone would yield a lime suitable for the ordinary purposes of the house builder. The analysis shows a deficiency of alumina, which indicates slow setting, but its ultimate induration is not thereby affected.

No. 22. Grey shelly limestone from Southland, locality unknown. Although the analysis is not complete, it shows this to be a very good lime of its class, probably the best hitherto discovered in Southland.

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No. 23. White granular stone from the Oamaru district. This is the well-known building stone. So far as can be judged from the analysis, it would furnish a much better lime for building purposes than the stone usually burned in the locality.