The Pamphlet Collection of Sir Robert Stout: Volume 2
I. Extracts from what has already been published on the subject, with Remarks
I. Extracts from what has already been published on the subject, with Remarks.
In the Seventh Annual Report on the Colonial Museum and Laboratory, published in 1872, No. 1230, is a valuable hydrous hematite ore from Para-para, Collingwood, but it unfortunately occurs intermixed with quartz pebbles, being, in fact, the cementing material of a bed of conglomerate, at least 100 feet thick, which extends for about 1,000 yards at the surface. If by hand-picking a large amount of iron ore could be obtained equal to the sample analyzed, the deposit would be a valuable one.
|Sesquioxide of iron
The amount of metallic iron in the sample received would be about 44 per cent. A very good pigment, especially adapted for ironwork, is manufactured from this ore.
Remarks.—I cannot quite agree with what is said about the occurrence of quartz pebbles, and the necessity for picking the ore. There are many places in which a quartz pebble is a rarity, and if the quarry were commenced in a judiciously chosen position, it would, I think, be unnecessary to exercise any great care in selecting the ore. This would have to be in page 51 the upper portion of the deposit, as the stone there seemed to me much more free from impurities.
The length of the deposit within the boundary of the lease, as shown in the accompanying plan, is 2,772 yards, and I think it runs right across the country to Onakaka Creek, a distance of more than a mile from the boundary: its average thickness is, I think, over 200 feet.
"Para-Para Iron Ore."
As intimately connected with the value of the Parapara iron ore, I give an analysis of some iron produced from it at Melbourne in the latter end of 1873.
|Carbon, free (graphite)
|Silicon, with titanium traces
Physical Characters.—Colour uniform, approaching white; structure homogeneous, and finely granular; hard, brittle.
From the character and analytical results above cited, it will be seen that this sample is of the variety technically known as white iron. It is comparatively free from phosphorus, but contains sulphur in some quantity, though not greater than is found in many pig irons smelted from the same class of ore which has furnished the present specimen.page 52
|Protoxide of iron
|Sesquioxide of iron
|Oxide of manganese
|Sulphide of iron
|Silicate undecomposed by acids
"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 a mixture, 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."
Remarte.—I have noticed the quartz pebbles else page 53 where, and would merely suggest the alteration, "Most of it is free from such admixture."
With reference to the above amount, viz. 15,000,000 tons, which is so very much under my estimate, the small amount includes only what is available by surface-excavation. The larger figure represents my estimate of the total quantity.
In a memorandum from Dr. Hector to the Colonial Industries Committee, in 1873:—"No. 9 is from a deposit of hydrous hematite that occurs in the Upper Tertiary drifts at Para-para, in the province of Nelson, but is also not infrequent in many other localities."
The ore occurs as the matrix of the quartz conglomerate, but often containing large masses of nearly pure ore, several hundred pounds in weight. On breaking these, there is frequently a kernel of undecomposed sulphide of iron, showing the origin of the ore is probably from the denudation of a mineral vein.
"I produce to the Committee a piece of wrought iron made from the above ore. I consider it of first-rate quality; it was twisted and bent cold in my establishment this morning."
It may not be out of place to give a short extract from the publications of the Second Geological Survey of Pennsylvania, by Mr. F. Prince, Junr., Assistant-Geologist.
"Description of the Brown Hematite on ranges of Lehigh County.
"The great bulk of the iron ore found in the dolomite or limestone is known under the names of Limonite or Brown Hematite. It is the hydrated ferric oxide, having the formula 2Fa3 Oz3 H2 O, containing when pure 59 89 per cent, of iron.
"The ore occurs massive, earthy, botryoidal, mammillary, concretionary, and occasionally stalactitic. It page 54 has a silky, often a submetallic, lustre, sometimes dull and earthy; colour of surface of fracture, various shades of brown, commonly dark, and none bright; when earthy, brownish, yellow, ochre-yellow. The streak is yellowish-brown. When stalactitic, it forms pipe ore, which is rather scarce; when concretionary it forms hollow spherical masses, commonly known under the names of pot or bombshell ore. These hollow masses commonly contain water or masses of unctuous clay; their interior surface often presents a glazed appearance, due to a very thin coating or incrustation of oxide of manganese, which imparts a nearly black varnish-like surface. Sometimes the bombshell is solid; its interior then presents a honeycombed appearance, as if from the percolation of chalybeate water into the mass after the exterior shell had been formed."
This is an admirable description of the Para-para hematite, but I did not find it stalactitic. The per centage of metallic iron in various samples of the Lehigh stone is almost the same as that of the Para-para.
"Many persons have supposed that the limonite was formed by the oxidation of iron pyrites. It is to be noted as a fact rather opposed to this view, that, with one exception, it has been found impossible thus far to find iron pyrites in any of the mines examined. That exception is at Thomas Breiing's mine, and there the pyrite is evidently of later age than the limonite, and has a stalactitic appearance. Some persons, on the other hand, have supposed that the ore was formed by the alteration of carbonate of iron, which has been found in some cases present in the limestone. Still others have supposed the ores to be the result of reaction between the limestone and ferrous sulphate."
As yet all of these theories are mere hypotheses, and before the correctness of all or more of them can be proved, it will require a long series of chemical investigations.page break