80 



ARTIFICIAL PRODUCTION OF SIMPLE MINERALS. 



ic (and pyroxenic ■?) rock, with the appearance 

 of dolomite, of gypsum, and of rock-salt(25*). 

 Everything in the phenomena here referred to 

 proclaims the influence of subterraneous forces 

 upon the sedimentary strata of the ancient 

 ocean. 



The beds of pure quartz of enormous magni- 

 tude, which are so characteristic of the Andes 

 of South America(2") — ^^^^ j ^ay here state 

 that I have seen such beds between 7 and 8,000 

 feet in thickness, in the route from Caxamarca 

 to Guangamarca, descending towards the south- 

 ern ocean — are of enigmatical origin. They 

 rest in one place upon quartzless porphyry, in 

 another upon dioritic rocks. Have they been 

 produced from sandstone, as M. Elie de Beau- 

 mont conjectures has been the case in regard 

 to the quartz strata of the Col de la Poisson- 

 niere, to the east of Brian9on'!("®) In the di- 

 amond districts of Minas Geraes and St. Paul, 

 in Brazil, which have been lately so carefully 

 examined by Clausen, Plutonic forces acting 

 upon dioritic veins have developed in one place 

 common mica, in another ferruginous mica, in 

 the quartzose itacolumite. The diamonds of 

 Grammagoa are contained in layers of solid si- 

 licic acid ; occasionally they lie enveloped by 

 plates of mica, exactly like the garnets formed 

 in mica-slate. The most northern of all the 

 diamonds which have been found since the year 

 1829, under the 58th parallel of north latitude, 

 on the European declivity of the Ural mount- 

 ains, also stand in geological relation to the 

 black carboniferous dolomite of Adolfskoi(2*^), 

 as well as to augitic porphyry, which have not 

 yet been made the subject of sufficiently accu- 

 rate observations. 



Among the most remarkable contact-phe- 

 nomena, finally, are comprised the formation 

 of garnets in clay-slate, under the influence of 

 basalt and dolerite, instances of which occur in 

 the county of Northumberland and in the island 

 of Anglesea ; and for the production of a great 

 number of beautiful and very dissimilar crys- 

 tals—garnets, Vesuviane, augite, and Ceylanite 

 — which make their appearance upon the con- 

 tingent surfaces of eruptive and sedimentary 

 rocks, on the boundary of the syenite of Mon- 

 zon with dolomite and compact limestone("^). 

 In the island of Elba, the masses of serpen- 

 tine, which nowhere, perhaps, present them- 

 selves so conspicuously as eruptive rocks, have 

 caused the sublimation of iron glance and red 

 iron stone into the fissures of a cretaceous 

 sandstone("9). The same iron glance is still 

 seen every day, sublimed from vapour, upon 

 the edges of open fissures in the craters of 

 Stromboli, Vesuvius, and ^Etna, and in cracks 

 of the recent lava streams of these volca- 

 noes("°). As we here perceive the materials 

 of veins produced under the influence of volcan- 

 ic forces before our eyes, and where the neigh- 

 bouring rock has already attained to a state of 

 solidity, we conceive how mineral and metallic 

 veins may have been produced during the ear- 

 lier revolutions of the crust of the earth ; when 

 the solid, but still thin shell of the planet, re- 

 peatedly shaken by earthquakes, shattered and 

 rifted by alterations in its volume occasioned by 

 cooling, presented numerous communications 

 with the interior, numerous outlets for vapours 

 laden with earthy and metallic substances. 



1 The stratified arrangement of the mineral 

 ! matters parallel with the surfaces bounding 

 veins, the regular repetition of similar layers 

 on both sides, on the roofs and on the floors of 

 veins, and the druses or elongated cavities of 

 their middles, indeed, frequently bear imme- 

 diate testimony to a Plutonic process of subli- 

 mation in metalliferous veins. As the matter 

 traversing is of more recent origin than the 

 matter traversed, we learn from the relations 

 of position of the porphyry to the silver-ore 

 formations of the Saxon Erzgebirge, that these, 

 in the mountains which are richer in mineral 

 treasures than any others in Germany, are at 

 least younger than the trunks of trees of the 

 coal formation and than the lower new red 

 sandstone (Rothliegendes) ("^). 



All our geological speculations, in regard to 

 the formation of the crust of the earth and the 

 metamorphosis of rocks, have had unexpected 

 light thrown on them, by the happy idea of as- 

 similating the production of scoriae in our smelt- 

 ing furnaces, to the formation of natural min- 

 erals, and of reproducing these artificially from 

 their elements(^"). The same affinities, de- 

 termining chemical combinations, come into 

 play in all these operations, whether they be 

 conducted in our laboratories or in the bosom 

 of the earth. The most important simple min- 

 erals, characterizing the very generally distrib- 

 uted Plutonic and volcanic rocks, as well as 

 those that have suffered metamorphosis through 

 them, have been found in our artificial mineral 

 formations in the crystalline state, and like the 

 natural ones in all respects. We distinguish 

 those that have arisen accidentally in scoriae, 

 from those that have been produced intention- 

 ally by chemists. To the former belong fel- 

 spar, mica, augite, olivine, blende, crystalline 

 oxide of iron (iron glance), octohedral magnet- 

 ic iron, and metallic titanium(2^^) ; to the lat- 

 ter garnet, idokras, ruby (equal in hardness to 

 the Oriental stone), olivine, and augiteC***). 

 The minerals now named form the principal 

 constituents of granite, gneiss, and mica schist, 

 of basalt, dolerite, and numerous porphyries. 

 The artificial production of felspar and mica, in 

 particular, is of signal geological importance 

 for the theory of the formation of gneiss by the 

 transformation of clay slate. This contains the 

 elements of granite, potash not excepted("*). 

 It would not, therefore, be any thing very ex- 

 traordinary, as an acute geologist, M. von 

 Dechen, has observed, were we one day to find 

 a piece of gneiss produced upon the walls of a 

 smelting-furnace built of clay-slate and grey- 

 wacke. 



In these general considerations on the solid 

 crust of the earth, and after having indicated 

 three original forms of production in reference 

 to its mineral masses, viz., Eruptive, Sediment- 

 ary, and Metamorphosed rocks, there still re- 

 mains a fourth class, the Conglomerated, or 

 fragmentary, to wit. This title of itself brings 

 to mind the denudations or destructions which 

 the surface of the earth has suffered ; but it 

 also farther reminds us of the process of ce- 

 mentation or agglutination that has been ef- 

 fected by oxide of iron, and by argillaceous and 

 calcareous [and silicious] cements, by which in 

 one case rounded, in another angular, frag- 

 ments have been again united. Conglomerates 



