« ΠροηγούμενηΣυνέχεια »
ing from north to south, but having always a dipping inclination towards the east. These strata are moreover intersected by the veins of slate and calcareous spar, which serve as the matrices of the silver ore, in fissures bearing across the strata from east to west, and dipping towards the south. From all this, it would be evident that the whole formation belongs to the class of transition rocks which Von Buch has described as being so remarkable in this part of Norway; namely, transition granite reposing on transition limestone, and being itself intersected by veins of slate and limestone. But Von Buch speaks of “ the primitive mountains which surround Kongsberg':” and if we were to judge from detached specimens of the red granite, in which the veins of silver are found, we should be disposed to consider this kind of granite as belonging to the oldest class of primary rocks. We will endeavour to shew, by a rude cut, the Manner in manner in which the Kongsberg silver is found. Kongsberg The more antient or primitive fissures inter- deposited.
(1) “ The primitive mountains which surround Kongsberg stretch much less southward than we might well believe. Scarcely two English miles down, beyond the Dal-Elv, under the Church of Hedingstad, and before we come to Hellestad, the gneiss disappears under the dark bluishgrey fine granular limestone.” Travels through Norway, &c. p. 419. Lond. 1813.
CHAP. secting the strata are perpendicular; but those
which are now worked have an inclination towards the south. By the cut here afforded, it
will be seen that the silver, as it generally lies, is found in a vein of calcareous spar, and that this again occurs in a vein of schifver of slate. But there is a remarkable leader to the ore, without the presence of which the miners have little hope ; namely, iron pyrites and iron oxide: whenever the intersecting fissures contain these minerals, then silver is found; but if the pyriles and the iron disappear, the silver also fails; which is a very remarkable fact, as connected with the history of mining.
Every thing indeed belonging to the nature of these mines is worth the most scrupulous attention; because mines of native silvér, although not unfrequent in America, are the most rare in Europe: and among the very few instances in which such a
deposit has been observed, this of Kongsberg is the most conspicuous. When we came to the mouth of the shaft, a basket filled with the ore had just then been raised, which we eagerly examined. It consisted of native silver, disseminated in laminæ throughout masses of limestone spar, with dark veins of schistus; containing, in some instances, sulphuretted silver, and sulphate of barytes: the specimens were poor in precious metal, but served to give some idea of the produce of the mine; which is now an ore almost too poor for the operation of stamping; and now so rich, that the silver, as if it had been fused and drawn out into threads and capillary fibres, is seen in native masses, protruding beyond the surface of the stone'. Sometimes the most beautiful arborisations, as they are called, of the native metal, are exhibited by contiguous crystals of native silver, in octahedral and in cubic forms.
We descended into the mine by means of Descent ladders, as into the Cornish mines; being every- Mine. where struck by the proofs of the same inconsiderate expenditure of the public money, and the same waste among the works. There can
(1) See the Vignette to this Chapter; made from a specimen now in the author's collection, which he brought from the Kongsberg mines.
CHAP. be little doubt but that these mines would VIII.
become very profitable, if they were in private hands: and perhaps the best thing the Government can do, is to farm them out to individuals.
Besides native silver, these mines produce that very rare substance, the native electrum, or auriferous native silver.
We found it a very difficult thing to procure any tolerable specimens of this curious native alloy of gold and silver. When it occurs, the metal has a brassy aspect. We had a specimen of it, which we analyzed, containing, besides silver, nearly thirty per cent. of gold. Like the native silver, it is found in laminary and capillary forms; and sometimes, but very rarely indeed, it is crystallized in cubes. The other minerals found here are noticed below, in the note': with the
(1) 1. Sulphuret of silver, massive and crystallized.
2. Red antimonial sulphuret of silver, ditto.
exception of the ores of copper, the specimens of CHAP. which are exceedingly rich; but they are not sufficiently abundant to make this metal an object of research, otherwise than for the silver with which it is combined.
We descended into the mine by ladders nearly perpendicular; meeting with occasional landingplaces, in our way down. At the depth of a few hundred feet, the veins of silver were occasionally pointed out to us; but those which we saw were so poor, that they could scarcely be discerned by any but a miner's eye. The richest veins are those which dip towards the south: and they are especially rich when they occur associated with the sulphuret of iron, or pyrites ; called, by our Cornish miners, Mundic. The ore, and all the rubble of the mine, were drawn up by a water-wheel, at the distance of four or five hundred yards from the mouth of the shaft; the communication being carried on the whole way by cumbrous machinery. From the spot where this shaft has been opened, we had a fine view of Kongsberg and of the surrounding country.
After a most laborious investigation of the
(2) It is nevertheless collected, after being separated, and in considerable quantities, from the basons in the smelting-works: the pure copper being made into cakes of the same size and form as are those of the silver. VOL. X.