THE FARMER'S MONTHLY VISITOR. 



116 



pyrites are among the most common of the min 

 erals which occur in that rock. 



Garnets occur in red or brownish red crystals, 

 having tl)eir primary form the rhombic dodeca- 

 hedron, and witli secondary planes produced by 

 replacements of the edges of the primary crys- 

 tal. 

 Its sp. gr. is from 3.90 to 4.236. 

 It melts beibre the blow-pipe into a black glo- 

 bule which is generally magnetic, owing to the 

 presence of the protoxide of iron. 



The precious garnet of Bohemia consists, ac- 

 cording to the analysis by Vaquelin, of 



Silica 3U.0 



Alumina 22.0 



Prot-ox. Iron 36.8 



Lime 3.0 



97.8 



Finely crystalized garnets occur abuudantly in 

 the rocks of New-Hampshire, but they rarely 

 possess a sufficiently rich color to render them 

 valuable in jewelry. 



There are numerous species and varieties of 

 garnets which possess different colors, according 

 to the natm-e and iirojiortions of the metallic ox- 

 ides which they contain. 



Thus a light green variety contains a very large 

 proportion of lime, and but little oxide of iron, is 

 called from its color, grossular (or gooseberry 

 green garnet.) 



Tlie black garnet, or melanite, owes its dark 

 color to the presence of a large proportion of the 

 per-oxide of iron. 



Spessartine or manganesian garnet is highly 

 charged with prot-oxide of manganese, to which 

 its color is partly due. 



TocRMAUNE. This mineral presents a great 

 number of varieties, which possess different col- 

 ors, owing to the replacement of one metallic ox- 

 ide by another, and by their variable mixture. 



The essential ingredients may be stated in 

 general terms to be silex, alumina, and boracic 

 acid with different metallic oxides. 



The most common variety is the black tourma- 

 line, commonly called schrol. It abounds in the 

 primary rocks, and is sometimes mistaken for 

 coal, on account of its apparent resemblance to 

 anthracite. The want of combustibility is, how- 

 ever, sufficient to distinguish it from that sub- 

 stance. 



Black tourmaline consists, according to Gme- 

 lin, of 



Silex 37.65 



Alumina 33.46 



Potash and Soda 2.55 



Magnesia 10.98 



Oxide 9.38 



Boracic acid 3.83 



It melts Vi-ith difficulty before the blow-pipe, 

 and forms a brown or black enamel. 



Its specific gravity is from 3 to 3.43. 



It scratches quartz, but is softer than topaz. 



Some varieties of the tourmaline are strongly 

 electric when heated. 



Bervl is an abundant mineral in New-Hamp- 

 shire, and occurs in granite rocks. The largest 

 specimens known in the world were obtained 

 rroiii Acwonh. Smaller but very perfect crys- 

 tals aie found in Grafton and in Alstead. 



Beryl is a variety of emerald, differs from that 

 gt-m only in the want of the rich green color due 

 to a minute quantity of chromic oxide. 



Bervl of Siberia, analyzed by Klaprotk, con- 

 sists oif 



Silica 66.45 



Alumina 16.75 



Gliicina 15.50 



Oxide of Iron 0.60 



The Emerald of Peru consists of 



68.50 

 15.75 

 12.50 

 0.30 

 1.00 



Alumina 

 Glucina 



Oxide of Chlorine 

 Oxide of Iron 

 Bei7l crystallizes like the emerald in the form 

 of six sided prisms, terminated by plane sum- 

 mits. The terminal ed.jes and angles are not un- 

 frequently replaced by tangent ])lanes which 

 rarely cover the plane termination. Its specific 

 gravity is 2.7. 



It scratches quartz with difficulty, and is 

 scratched by the topaz. 



It melts with difficulty before the blow-pipe 

 flame into vesicular glass. In another section 



of this Report will be seen an analysis of the 

 Beryl from New-Hampshire. 



Iron Pyrites, or the Bi-sulphuret of Iron, is 

 a very common mineral, and is often mistaken 

 by persons unacquainted with minerals, for Gold, 

 Silver or Brass, according to the accidental tints 

 which it may possess. 



It has generally a whitish gold yellow color, 

 crystalizes in right square prisms, nearly appio.xi- 

 mating to the cube or in cubic Ibrins. Its spe- 

 cific gravity varies from 4.6 to 5. 



When heated before the blow-pipe, it burns 

 with a blue flame, and the odor of burning sul- 

 phur is perceived. 



The globule remaining after fusion upon char- 

 coal, is theproto-sulphuret of Iron, and is strong- 

 ly magnetic. The globule is not malleable, hut 

 breaks into brilliant fragments of a white color, 

 having a metallic lustre. If a little diluted sul- 

 phuric acid is poured upon its powder, the odor 

 of sulphuretted hydrogen is at once perceived. 

 By these tests any one may learn to distinguish 

 this mineral. 



According to the analysis of Berzelius, Iron 

 Pyrites consist of— 



Sulphur 54.26 



Metallic Iron 45.74 



Or of one equivalent of Iron to two of Sul- 

 phur. 



There are many varieties of Pyrites, some of 

 which contain Arsenic, Cobalt or Copper in va- 

 riable proportions, the sulphurets of their met- 

 als being capable of replacing a |)ortion of the 

 sulphuret of Iron. 



Brown Pyrites sometimes contains minute par- 

 ticles of metallic Gold, or of Silver, intermixed 

 with its substance or included in the fissures and 

 strata, and thefineparticlesof gold appear when 

 the crystals of pyrites decompose. Auriferous 

 pyrites occur in Virginia, N. Carolina, in Geor-. 

 gia, and also in the Ural mountains of Siberia. 

 No gold has yet been found in the Brown Pyrites 

 of New-Hampshire. 



Copper Pvrites, or the sulphuret of Copper 

 ud Iron, is a valuable mineral. It occurs in 

 considerable abundance in New-Hampshire. 



It may be distinguished easily by the following 

 properties. It is much softer than Iron Pyrites, 

 and is easily cut by the knife, while Iron Pyrites 

 is found to be \ery hard and brittle. 



Copper Pyrites, when pulverized and dissol- 

 ved in nitric acid, may be tested for copper by 

 plunging a polished piece of steel into the acid 

 solution, when metallic copper will precipitate on 

 the surface of the steel. Or the clear solution 

 may be super saturated with Ammonia, when the 

 oxide of Iron will be thrown down as a brovvn 

 precipitate, and the su|.'er-natant solution will 

 have a fine azure blue color, since it contains all 

 the oxide of copper in solution. 



If Copper Pyrites is roasted on charcoal be- 

 fore the blow-pipe, so as to exj>el most of the 

 sulphur, and is then melted with carbonate of so- 

 da, globules of metallic copper may be separa- 

 ted, and will be seen on the surface of the char- 

 coal. 



Pure copi)er pyrites consists of— 

 Sulphur 35.87 



Metallic Copper 34.40 



Metallic Iron 30.47 



or of one equivalent of Copper, one of Iron, and 

 two of Sulphur. 



The above descriptions may be of service to 

 persons who wish to investigate the nature of 

 such minerals as occur associated with the pri- 

 mary rocks. 



There are many others which are occasionally 

 found in this class of rocks, but for want of room 

 in this introduction, I must refer the reader to 

 special works on Mineralogy. 



G.'JEISS. 



In the ascending order, we come next to a rock 

 composed of the same minerals as Gratiite, but 

 which is more or less distinctly stratified in 

 its structure. It is known under the name of 

 Gneiss. 



It reposes directly on Granite, and may be 

 considered as a variety of that rock. Owing to 

 its stratified structure. Gneiss splits parallel to 

 the planes of the mica, and large slabs may be 

 readily obtained. 



It is extensively used for building and for stone 

 walls. The more compact varieties are com- 

 monly sold under the nain« of Granite. 



Some Geologists consider Gneiss to be a me- 

 tamorphic rock, and as having been originally 

 formed by sedimentary deposit from aqueous 

 suspension. Others suppose that its stratified 

 structure is due to crystalization in laminte, and 

 that it is merely the upper crust of Granite. 



If Graphite, (or black lead) originated exclu- 

 sively from vegetable matter, there is reason to 

 believe that the Gneiss once existed as u sedi- 

 mentary deposit on which vegetables grew, for 

 that mineral is not unfrequently found dissemi- 

 nated in the rock. The enormous thickness of 

 the strata seems to be an objection to the theory 

 of its metamor|)hic origin, for how intensely 

 heated must the Granite rocks have been when 

 erupted to have indurated strata several thousand 

 feet in thickness. Its origin is therefore yet an 

 undecided point in Geology, and one which may 

 hereafter be settled by the comparison of facta 

 observed at different places. New Hampshire af- 

 fords the best opportunities for the solution of 

 this problem, for nowhere in the country are there 

 such enormous and reiterated strata of this rock. 



The minerals included in Gneiss are similar to 

 those found in granite. Veins and beds of me- 

 talliferous ores also frequently occur. 



Mica Slate is composed of the minerals mi- 

 ca and quartz. The mica is dispersed in regular 

 layers, and is interstratified with fine grains of 

 quartz. 



It splits readily into sheets, the surfaces of 

 which are brilliantly plated with the crystals of 

 mica. 



When the lamina; are uniformly in the same 

 plane, the rock splits into large even tables, which 

 are highly valued for flagging stones, and they 

 are e.\tensiyely used for making side-walks in 

 our large cities. 



Mica Slate is generally considered a metamor- 

 phic rock, formed by the strong ignition of sed- 

 imentary deposits of the fine particles of gran- 

 ite from water. It exhibits a gradual passage in- 

 to Argillaceous Slate, which certainly is a rock 

 of sedimentary origin : hence we have reason to 

 believe Mica Slate was produced in the same 

 manner, it having been exposed to a more intense 

 heat, so as to form a decidedly crystalized aggre- 

 gate. 



The strata are frequently contorted and doub- 

 led over by the intrusion of Granite which has 

 been elevated through its mass. 



In this rock occurs a great abundance of val- 

 uable and curious minerals. Beds of Limestone, 

 veins of Iron, Lead, Copper, Tin, and Arsenic 

 ores. 



It is a highly metalliferous rock, and should be 

 e.xamined with great attention. I shall have oc- 

 casion hereafter to give a very full and complete 

 history of the minerals which occur in it in New 

 Hampshire. A sufficient number of example* 

 will be found in this Report to prove it to be one 

 of the most interesting rocks in the State. 



Chlorite Slate is of a dark green color. It 

 is soft, and is easily cut with the knilii, and when 

 freshly broken, may be scratched by the finger- 

 nail. It is not so unctuous as Talcose Slate. In 

 the fire it resists an ordinary red heat, but may 

 be melted at a higher temperature into a black 

 slag. When compact and free from quartz, it 

 may be turned in the lathe into various useful ar- 

 ticles, such as inkstands, vases, &c. 



The compact or crystaliue variety which oc- 

 curs in veins, is, however, preferable for this pur- 

 pose. It was from this mineral that the aboriginal 

 inhabitants of the Eastern States more frequent- 

 ly carved their stone pots and calumets. 



At present the Indians of Maine frequent the 

 Chlorite veins of Cross Island, for the purpose 

 of obtaining pipestone. 



It serves most perfectly for the purposes above 

 indicated. 



Associated with chlorite there frequently occur 

 fine crystals of Magnetic Iron ore, in the form of 

 the regular Octahedron. 



Beds of serpentine and soapstone often occur 

 beside those of chlorite, and their frequent asso- 

 ciation Seems to indicate a similar origin. 



Hornblende, Talcose, and Chlorite Slates of- 

 ten occur in situations analogous to Mica Slate, 

 and frequently alternate with the latter rock. 

 These rocks are easily distinguished by the pres- 

 ence of the minerals from which they derive 

 their names and characters. Hornblende Slate 

 is frequently charged with crystals of Garnet and 

 a few other accidental minerals, which will b« 



