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The Pamphlet Collection of Sir Robert Stout: Volume 2

Dr. Hector to the Hon. The Colonial Secretary

Dr. Hector to the Hon. The Colonial Secretary.

Geological Survey Office, Wellington,

Sir,

I have the honour to report that, in consequence of my having received information to the effect that several faults or page 39 dislocations of the strata had been encountered in the tunnel which is being driven to explore the coal-measures at the Collingwood Mine, I took the opportunity of the "Luna's" visit to the Spit Light to land at Collingwood and inspect the work. The tunnel is now in 400 feet, and the following is the section of the strata passed through:—
Feet.
1. Tough sandstone and breccia, with carbonaceous matter 165.0
Dip 19° to W.
2. Coal, clean and bright .5
3. Sandstone band 2.0
4. Coal, clean and bright 1.2
5. Sandy shale 2.5
6. Ironstone 1.0
7. Sandstone, with bands of grit. Fault. Downthrow to W. 18 inches 28.0
8. Sandstone and breccia. Dip 12° W. Fault. Downthrow to S.W. 18 inches 39.0
9. Dark sandy shale with films of coal. Dip 30° to W. 18.0
10. Ironstone 1.4
11. Coal, not clean .5
12. Sandstone .7
13. Coal, clean .8
Dip 30° to W., and passes under a thick mass of
14. Dolomite of magnesia limestone, passing into breccia of the same. Contains carb. of lime, 53 per cent.; carb. of magnesia, 44 per cent. 15.0
The coal then rises again in the floor of the drive, and 10 to 13 are again cut with dip 16° W.
15. Tough carbonaceous sandy shale. Dip 10° to N. 30 W. 27.0
16. Coal mixed with shale 4.0
17. Ironstone 1.0
Fault. Downthrow 9 feet to W. at 45°.
18. Tough crown carbonaceous sandstone, not bedded 45.0

The coal seam (16) was cut only in the roof of the drive, and, had the level of the drive been a few feet lower, it would have been missed altogether. On the other hand, had the level been even a few inches higher, the true nature of the dolomite (14) would not have been ascertained, and it might have been taken for a dyke instead of a local variety in the stratified rock forming the cover of the coal.

The only fault of any importance is that occurring at 17, and its effect will be to shorten the length of the drive required to cut the page 40 main coal by about 50 feet, and also thereby avoid the cutting of some of the hardest rock that had to be excavated in the course of the work.

I have therefore to report that the work is progressing even more favourably than was anticipated. The rate at which the drive is advanced averages 2 feet per day, and the distance which still remains to be driven, in order to cut the main coal, is about 200 feet.

As I returned from Collingwood I took the opportunity of reexamining the deposit of brown ironstone at Parapara, and found that my former estimate of its extent is nearly correct.

The ore occurs as large patches in a stratum of gravel. The greatest thickness of the stratum is 100 feet, and the area of the patches of ironstone showing at the surface is about 100 acres.

The ironstone weathers to a dark colour, and covers the surface of the hills with blocks of all sizes up to many tons in weight A rough estimate made on the spot gave the quantity of ore available by mere surface excavation as at least 15,000,000 tons.

The ironstone everywhere shows traces of its origin as a bog ore that was deposited as a cement among gravel, as it contains rolled pebbles of quartz; but much of it is free from such admixture, and by hand-picking, and a simple modification of the smelting process, much of the siliceous matter could be eliminated, and the ore profitably smelted.

All the varieties of iron ore occurring at this place, and also at the coal mine, were collected on this occasion, and will be reported on as soon as they have been analyzed.

I have,&c

James Hector,

The Hon. the Colonial Secretary.