« ПредыдущаяПродолжить »
and to these we will confine our attention at present, They
Magnetite Fes 04 (=metallic iron 72.4 per cent.) not common in England ; occurs abundantly in Sweden, and is used for making the famous Swedish iron.
Hematite Fe, Og (=metallic iron 70 per cent.) largely worked near Barrow and Ulverston and used for the manu. facture of Bessemer steel.
Limonite, or Brown Iron Ore 2Fez 08, 3H, 0,=(metallic iron nearly 60 per cent. when pure), a widely distributed and abundant ore. That from Lincolnshire and Northamptonshire yields 32 to 37, South Wales 41, and north of Spain about 55 per cent, of iron. The Forest of Dean ore probably contains some Hematite mixed with it as it yields about 63 per cent. of iron.
Siderite or Spathic Iron, Fe.C.08 (=metallic iron 48 per cent. ) not much worked in England, but is used in Styria and yields 34 to 48 per cent. iron. Clay Ironstones are im. pure carbonates, and are extensively worked in Wales, Staffordshire, Shropshire, Derbyshire, Yorkshire, Cleveland, and Scotland, and yield from 26 to 41 per cent. iron. Another variety, the famous Blackband, worked in Scotland, North Stafford, and South Wales, yields 29 to 42 per cent, iron, and contains 20 to 25 per cent. coaly matter.
The carbonates are by far the most important ores worked in Great Britain, and out of fifteen million tons of iron ore mined in 1881 nearly twelve millions were of this class. Although the percentage of metal contained in them is not usually very high, they are kindly ores to smelt, and are found either in the coal fields or very near thereto, and often in immense quantities, as at Cleveland, under conditions permitting them to be mined at a low cost. The two most essential raw materials used in the manufacture of iron being heavy, bulky, and of low value, and consequently unable to bear heavy costs of handling, or large transit charges, their juxtaposition has materially influenced the location of the industry in Britain, and we find all our old centres of iron
coal fields. And similar condicions will most likely affect the localisation of the manufacture in New Zealand whenever the time arrives at which that manufacture can be undertaken with good prospects of success. In our survey of the country we will therefore follow the order we have adopted in describing the coal deposits, beginning with the North Auckland district.
Near Wangarei in the Whau-Whau valley there is a hill said to consist in large part of Hematite, and in a borehole south of Mount Tiger a bed of ironstone 67 feet thick was proved to be resting on the limestone. At Hikurangi iron ore exists, and at Kawau a brown iron ore occurs in considerable abundance, a sample of which yielded nearly 68 per cent.
. iron oxides (48 per cent. iron). At Tararu Creek, Coromandel, Hematite is found in abundance and is now being extensively manufactured into iron oxide paint.
South of Auckland and near the Waikato Coal field both oxides and clay ironstones are found. Near Drury and Hunua and at Raglan there are large deposits of granular magnetite cemented by iron oxides into compact mass. At Maramarua is a deposit of hematite with some magnetite, and brown iron ores in balls are abundant in the coal measures near Raglan. Overlying the coal at Miranda Colliery are bands of clay ironstones. Abstract analyses of Waikato Iron Ores :
Metallic & earthy
Near Taranaki a clay band is found yielding 39 per cent. iron; and a similar kind of ore at Manawatu Gorge, Wellington, contains 38 per cent. iron.
In the South Island, Nelson province is rich in iron ores. At Dun Mountam and in the Mataura Creek Hematite has been found. At Parapara, near Collingwood, is an extensive deposit of Brown ironstone which has attracted considerable notice and given rise t) many sanguine dreans of a future Cleveland in the Southern Hemisphere, only so far to end in disappointment. It resembles a quartz conglomerate, cemented by hydrous iron oxides, but in many parts the ore is almost pure. Large boulders of ore are strewed about the surface, and, for reasons which he gives, and which certainly appear to justify his opinion, Mr. Cox concludes that this is the “iron hat" or gossan of a very large pyritous lode. The quantity of ore is variously estimated at from fifteen to fifty-two million tons. Analysis shews 62.68 iron oxides (equal to 44 per cent.iron.) Portions of this deposit are now being worked for the manufacture of Iron Oxide paint. In the drive at Collingwood Coal Mine several beds of ironstones, somewhat resembling Blackbands, are associated with the coal seams. Two samples gave 61 and 45 per cent. iron oxides (=45 and 35 iron) with 5 to 18 per cent, coaly matter. It will be remembered that the coal from this mine makes good coke, and limestone being also available, attempts have been made to work these deposits. A large amount of money has been expended, possibly not in the most judicious manner, for no success has been attained and the works have been abandoned. A bed of brown hematite is reported to exist at Mount Peel, associated with beds of compact blue limestone. It is of considerable extent, about 50 feet in thickness, and contains 54 per cent. metallic iron. Near Westport are spathic iron ores ; and near Grey River nodular masses of clay ironstones are plentiful in the coal measure shales. Of their quality the author has no information, but their proximity to the excellent coking coals of the Grey district would seem to indicate them as worth further examination. At Abbey Rocks spathic iron ore with 26 per cent iron has been found ; and hematite from near Paringa River gave 58 per cent. metallic iron.
In Canterbury at Mount Somers, at Malvern Hills, and at Waipara are extensive deposits of clay ironstones, but rather remote from suitable coal; and at Wakatipu Lake, Otago, are several veins of hematite in mica schist : one of 6 feet thick, containing sesquioxide of iron 96.11 per cent. (=68.8 per cent. iron) with siliceous matters 3.89 per cent.
The available information as to the iron deposits is neither so full nor so definite as a practical man would desire ; the attention of the officers of the Geological Survey does not appear to have been specifically devoted to this enquiry (except in the case of the Parapara deposit), nor does there appear to have yet been any systematic examination made with a view to ascertain if the conditions necessary for successful iron making exist. So far as our present knowledge goes, we
see that in North Auckland there is iron ore, good coal, and limestone in close contiguity; in Waikato, good iron ore, limestone within easy reach, and coal which, though inferior to that used in England, is yet equal to much that the Germans use successfully for iron-making; at Collingwood, is good ore and limestone, and the coal is of suitable quality if it can be found easily accessible and in sufficient quantity; at the Buller and Grey is good coal and limestone in the vicinity, if the ores prove to be sufficiently abundant, and if they can be got cheaply ; so that it appears not unreasonable to believe that the iron manufacturer may yet establish himself in New Zealand and flourish.
Iron Sands.-From early days the iron sands which occur so plentifully throughout the colony have attracted great notice. The beach at Taranaki, between tide marks, almost wholly consists of black titaniferous iron sand for many miles in length and many feet in depth, and numerous trials have been made to utilise this deposit. It was long believed that titanium imparted some wonderful properties to the steel made from ores containing it, but this idea is now very generally questioned. No practical success has resulted from attempts to utilise iron sand for making cast iron; but in America a kind of Catalan forge is used by which such sands
are converted directly into wrought iron.* Along the West Coast black sands are abundant and are auriferous; and they occur at many other points on the coasts. They are also of very general occurrence in the river beds, and even the gravels and sands when “panned ” will often yield them. Though these iron sands are not likely to be of much commercial importance, they are of interest scientifically. They are evidently the result of rock disintegration ; those derived from the Diabase and Granite consist largely of Magnetite ; those from the Hornblende and Mica Schists, and Paleozoic Slates are chiefly Hematite and Magnetite ; while the sands containing Magnetite and Ilmenite are from the Trachytes, Basalts, and Diorites.
Iron Pyrites is of very common occurrence. It is disseminated in small crystals in the Tufanites of Coromandel and in many of the metamorphic schists of the South Island. It is also a common constituent of the various lodes and reefs and is frequently auriferous. In the Parapara River, Collingwood, there is a lode of compact pyrites 8 feet wide, and at Mount Rangitoto is a pyritous lode carrying also galena and gold. Pyrites and Marcasite occur rather too plentifully in the Brown Coal seams of the eastern districts of the south Island, where they are decidedly de trop, as they have no doubt been active agents in causing the many cases of spontaneous combustion which have afflicted the owners of collieries working those seams. Pyrites are used for the manufacture of Sulphuric Acid and Green Copperas, but the writer is unable to say if either of these industries is carried on in New Zealand.
* By latest advices (February, 1883) we learn that an attempt is being made at Onehunga, Auckland, to manufacture “blooms'by the American direct process from the beach sands at Manukau, under the stimulus of a Government bonus of £1000 for the first 200 tons of blooms.