페이지 이미지
PDF

Sussex county, New Jersey, together with a list of the minerals found at that interesting locality. We proposed furnishing the Academy with a description of some of these minerals; but, from a multiplicity of other engagements, we have been prevented from completing our examination of a substance which we believed new, and to which we gave the name of Dysluite. We hope soon to be able to present it to the Academy, and in the meanwhile offer the following note on some of the accompanying minerals. 1. Jeffersonite.—As this mineral has been described in vol. ii. page 194, of the Journal, no further notice of it, at this time, would be necessary, except to describe some of its crystals, which has been o by Dr Troost, who, moreover, has shown at the same time, and by these crystals, that the Jeffersonite, which we believed to be a new species, appears in reality to be nothing more than a variety of the proteus of mineralogy, pyroxene. At the period at which our account of the Jeffersonite was written, we had no crystals of it; our specimens consisting merely of the lamellar variety. It was from the solid given by the lamellar fracture of the mineral, and from the absence of magnesia, which earth was regarded in some measure as an essential component of pyroxene, that we were induced to consider it as new. In justice to ourselves, it may be necessary to mention that, in mineralogy, the solid given by cleavage has, since the period of the publication of the Traité de Mineralogie, been considered next to composition, and faces deduced from the secondary forms, of paramount importance, and sufficient of itself, in the absence of the above named characters, to constitute or determine the formation of a species, of which we have several instances. The value attached to this character, by the late Abbé Haüy, is too well known to need any reference to his works; nor should it excite surprise, that so much importance has been given to this remarkable property in minerals, when we consider that this is the first anomaly which has come under our notice; for heretofore the cleavages, parallel to the faces of the primitive form, have invariably been the smoothest and easiest to be obtained. Whence the cause of this deviation from so general a law, we know not; future observation must determine it. Mr Seybert has analyzed a variety of the same mineral, which has yielded him four per cent. of magnesia. Whether this be accidental or not, we are not prepared to say. All the analyses of pyroxene, noticed by the Abbé Haüy in the

last edition of his Treatise on Mineralogy, state the quantity of that earth to be from ten to nineteen per cent., which far exceeds Mr Seybert's results. . Mr Rose's analyses of pyroxenes are, it is true, of a much later date; but when we recollect the great confusion which exists in this species, we may be permitted to question whether the substances, which he examined, were really pyroxenes. Of those analyzed by Vauquelin and Laugier, no doubt can exist, since the analyses were made at the Garden of Plants in Paris, and, as it were, under Haüy's eye. But the examination of the crystalline forms certainly puts the question of the identity of the Jeffersolite and pyroxene at rest. 2. FRANKLINITE.-The Franklinite forms a mass whose immense extent has been made known in the geological part of our communication. Apparently, it is not perfectly homogeneous in composition throughout; the proportion of manganese which it contains seems to vary, and produces a corresponding variation in the colour of its powder, and in the different effects which result from weathering; nor is it less variable in its extermal appearance, being in masses, grains of different size, and crystals. The large masses present numberless druses, in which the ore has either assumed a regular form, or endeavoured so to do, but has been disturbed while in the act of crystallizing. Its form is the regular octohedron, with deepl marginated edges, presenting a passage into the ...{ dodecahedron. The ...i. vary in dimension from the microscopic size to two or more inches in length. The smallest and most numerous are found at Franklin, and the largest at Stirling. The crystals have a fine metallic lustre, of a black colour, opaque, without any indication of cleavage. . Specific gravity 4.98 to 5.08. 3. RED zinc ore (improperly called red oxide of zinc). This mineral occurs in several places in the mass of Franklinite; but it is at Stirling that it is found not only in the greatest quantity, but in the purest state; the abundance of this mineral is such at this locality, that it will at no distant period be worked for zinc ; this ore has not yet been found in crystals, or unmixed with Franklinite. According to Mr Mohs' obserVations, it presents an imperfect cleavage which connects it with a prismatic system. On breaking the red zinc ore of Širling, we find two kinds of particles as to size and colour; The largest ones are of an almost ruby red, with considerable lustre, resembling in some measure that of the diamond, and *transparent as to admit of a ready passage to light. The *out of the smaller ones, which are fine granular, is of a beautiful dark orange, and of so little lustre as at first sight to induce a belief of their being in an earthy state; but if examined with attention, the effect is observed to arise from interposed light, for no difference can be perceived between them and the larger particles, when examined individually. If both be o their powder is the same, and is of a bright orange colour. When the red zinc ore has been a long time exposed to the atmosphere, the smaller particles are washed away, and the larger ones assume a deeper red. It likewise becomes coated with carbonate of zinc, and sometimes with an impure oxide of manganese; the former of these efflorescences may be discovered by its colour, its effervescing with nitric acid, and its producing a styptic salt. From the circumstance of the transparency of the red zinc ore, no doubt can exist with respect to its being a chemical combination of the oxides of zinc and manganese, such being the result of the analysis of Mr Berthier of the School of Mines. The iron, found in it by Dr Bruce, was owing to an admixture of Franklinite. At all the different localities of the red zinc ore, in Sussex county, it invariably accompanies the Franklinite, they mutually envelop each other; when the red zinc ore imbeds the Franklinite, the latter mineral is usually in the form of grains, which is particularly the case at Stirling. 4. CARBONATE or zinc. (Calamine). Besides coating the red zinc ore, this mineral is likewise found in very small veins or fissures, appearing to be of subsequent formation to the mass which encloses them. These veins are in the Franklinite, northeast of Franklin furnace. The colour of the carbonate is white, without lustre, and with little cohesion, owing to its particles being in an earthy state. 5. Siliceous oxide or silicate of zinc. (Calamine). This mineral is found both at Stirling and Franklin, but it is only at the former locality that it occurs in sufficient quantity to merit attention as an object of importance to manufactures. It presents itself in the form of concretions or grains, also in amorphous masses, and likewise in crystals. The concretions (which are the most common manner in which it exists) are evidently nothing more than the product of a disturbed crystallization; for every grade between them and the perfect crystals are observable. The form of the crystals is an hexagonal prism with dihedral terminations, the faces of which repose upon the lateral edges of the prism; the angles of the faces of the prism are 120°, and of the faces of the pyramid,

[ocr errors]

with one another, about 118° (?) being the regular o
prism with a rhomboidal summit, of course leading to a rhom-
bohedron for the primitive form; many of the crystals are an
inch in diameter, and two inches long; some are even much
larger. The faces and angles of the prism are generally well
defined, but it is extremely rare to find the pyramids well
determined, owing, in some cases to the convexity of their
angles; in others, of the faces themselves, and also to various
depressions and protuberances arising from different causes.
From these circumstances, we cannot positively affirm that
the terminal faces are those of a rhombohedron; particularly
as we have not been able to observe in the crystals any evi-
dent marks of cleavages parallel to these faces, nor, in fact, in
any other direction. The specific gravity of this mineral is
3.89 to 4.; it forms a jelly with strong acids, and is infusible
by the blowpipe.
The colour of the silicious oxide of zinc varies from a light
greenish yellow (which is the purest) to a deep flesh red; it
also occurs inclining to a green, brown, gray, and even to a
black colour, all of which are owing to variable admixtures of
Franklinite, garnet, pyroxene, &c. The colours are dull and
dirty; most of the crystals are covered with a brown ochrey
coating. In transparency it exhibits every degree, from the
highly translucent to the opaque; the most translucent is the
light greenish-yellow variety, which is the kind that exists in
grains, and is most abundant.
The associates of the silicious oxide of zinc are, at Stirling,
the Franklinite, the red zinc ore, the dysluite, carbonate of
lime, and mica; at Franklin, the garnet, pyroxene, &c.
Chemical part.—No loss, or any change whatever by cal-
cination, consequently anhydrous; decomposable by all the
strong acids; forming a jelly, owing to liberated silex. It was
sound to consist of silex and of the oxides of zinc, iron, and
manganese, the analysis having been made upon the flesh
coloured variety.
The modus operandi was to heat with nitromuriatic acid,
until a decomposition was effected, to evaporate to dryness in
order to set the silex free, then add acidulated water; the
liquor was, again, gently heated and filtered, which gave the
silex, leaving the metallic oxides in solution, from which the
oxides of iron and manganese were precipitated by ammonia
in excess. The zinc was then obtained from the solution.
The result of the analysis was,
WOL. II.-NO. 2. 18

Silex, . . . - - - - - - - 2544
Deutoxides of iron and manganese, . - - - - 6.50
Oxide of zinc, by difference, - - - - . 68.06

100.00

Another analysis, made by Mr Vanuxem, upon a purer variety, being crystals of a light flesh colour, yielded,

Silex, . - - - - - - - - - . 25.00
Oxide of zinc, . - - - - - - - - 71.33
Oxide of manganese, . - - - - - - . 2.66
Oxide of iron, . - - - - - - - - .67
Loss, . - - - - - - - - - - .34

~ 100.00

‘ole.—It is not improbable, from the different analyses and crystals which we have of the combination of oxide of zinc and silex, that there are two species, one hydrous, the other anhydrous.

ART. XX.-.An Account of the Earthquakes which occurred in Sicily, in JMarch, 1823. By Sig. ABATE FERRARA, Professor of Nat. Philos. in the University of Catania, &c. &c. [Translatea for this Journal by W. S. EMERson.]

ON Wednesday, the 5th of March, 1823, at 26' after 5 P.M., Sicily suffered a violent shock of an earthquake. I was losing in the large plain before the palace, in a situation where I was enabled to preserve that tranquillity of mind necessary for observation. The first shock was indistinct, but tending from below upwards; the second was undulatory, but more vigorous, as though a new impulse had been added to the first, doubling its force; the third was less strong, but of the same nature; a new exertion of the force rendered the fourth equal on the whole to the second; the fifth, like the first, had an evident tendency upwards. Their duration was between sixteen and seventeen seconds; the time was precisely marked by the second hands of a watch which I had with me. The direction was from northeast to southwest. Many persons who ran towards me from the southwest at the time of this terrible phenomenon, were opposed by the resistance of the earth. The spear of the vane on the top of the new gate connected with the palace, and upon which I fixed my eyes, bowed in that direction, and remained so until the sabbath, when it fell; it was inclined to the southwest in an

« 이전계속 »