scratched by quartz. It is very difficult to reduce it to powder. Its
fragments are sharp-edged, and have no regular form. It is slightly
translucent on the edges. Its powder is green; its specific gravity
3 *4 5 1 . Before the blow-pipe it becomes white and opake, and small
bubbles cover its surface, which burst when the heat is kept up. It
was this circumstance which induced Hisinger and Berzelius to give to
this mineral the name of pyrophysalite. The powder phosphoresces a
little when heated. This mineral according to the analysis of Berzelius,
is composed of the following constituents :
Alumina ............................................53*25
Silica . .......................... 32*88
L im e ............................................. o*88
Oxide of iron ............................. 0*88
Loss when heated to redness . . 0*75
Loss during the analysis 1 1*36
100*00
From the phenomena which this mineral exhibits before the blowpipe,
there can be little doubt that the enormous loss is owing to the
escape of some volatile acid. Nor can any other acid be suspected except
the fluoric. Hence there is every reason to believe that this acid
constitutes an ingredient in this mineral. In this respect it resembles
topaz and schorlous beryl, both o f which contain the same acid. Berzelius
points out the resemblance, in his paper on the Analysis of Pyrophysalite.
And Haiiy, from an ingenious examination and comparison
of the crystals, has considered himself entitled to conclude, that pyrophysalite
is nothing else than a variety o f topaz. There can be no
doubt that, as far as chemical analysis goes, the two minerals bear a
striking resemblance to each other.
6. In the same quarry at Finbo specimens of gadolinite have been
found, several of which I procured by the goodness of Assessor Gahn.
This mineral is very scarce, having been hitherto found only in two
places of Sweden, Ttterby and Finbo, and in both places in a rock belonging
to the species of granite. I f the same kind o f rock were properly
examined in other countries, there can be little doubt that it
would be found. A peculiar earth confined to a peculiar spot, and in
very minute quantities, can hardly be conceived. Yet that is the predicament
in which three of the earths stand at present, namely, zir-
conia, yttria, and glucina; while the other six are scattered in great
profusion through the rocks constituting the surface o f the earth.
7. In the same rock, at Finbo, and often mixed with pyrophysalite,
there occur small crystals, which are considered as crystals o f oxide of
tin. I do not know that they have ever been analysed. The opinion
of their nature depends upon their external characters. Perhaps in a
mineral so well characterised as tinstone these characters are quite sufficient.
But the smallness o f the crystals makes it difficult to apply
them with precision. Reduction before the blow-pipe upon charcoal,
assisted by borax, would be the simplest method of determining the
point. I am surprised that it has never been put in practice.
8. Sahlite has been likewise found about lo miles east from Fahlun,
in a copper mine called Bjorn-Myre-Sveden.
g. Besides these minerals there is still another which, as far as I
know, has not yet been described by any person. It has a reddish
yellow colour, and a certain degree o f resemblance to quartz; but is
very different in its properties. Not having been so fortunate as to see
this mineral, I cannot undertake to describe it. Specimens o f it were
sent me by Assessor Gahn, but I have not yet received them.
Besides the mine at Fahlun there are a considerable number o f other
mines in Dalecarlia. They are chiefly iron and copper mines, with one
or two lead mines, to which the Swedes give the name of silver mines,
because the galena is rich in silver, and the principal object of the
miner is to extract that metal. To this they in some measure sacrifice
the lead. Hence it happens, that the lead mines wrought in Sweden
are of little consequence in point of emolument; for it is seldom that
much profit can arise from merely extracting silver from lead.