Manual of mineralogy : including observations on mines, rocks, reduction of ores, and the application of the science to the arts : with 260 illustrations designed for the use of schools and colleges

Front matter

BERKELEY

LIBRARY

EARTH

CHAP. II. — CRYSTALLOGRAPHY: OR THE STRUCTURE OF MINERALS, 19 Secondary forms, . . . . . .34

Compound crystals, . . . • • .42

Dimorphism, . . . • • .44

Irregularities of crystals, . . • • .45

Measuring angles of crystals, . • . .47

Massive minerals, . . . • • .52

Columnar structure, . . . . .52

Lamellar and granular structure, . . .53

Pseudomorphous crystals. . . . • .54

CHAP. III. — PHYSICAL PROPERTIES OF MINERALS. Diaphaneity, — Refraction, and Polarization, . . 58

Phosphorescence, . . . . . .61

Electricity and Magnetism, . . . • .62

Specific gravity, . ' t . . . • .63

State of aggregation — Fracture, . . . .65

3. Carbon and compounds of carbon, r^»-* • • 80

1* vi

Contents

6. Earthy minerals, (silicates or aluminates,)

2. Lime,

1. Hydrous silicates,

Chap. IX. — Brief Notice Of Foreign Mining Regions, Chap. X. — Mineralogical Implements

CHAP. XL —WEIGHTS, MEASURES, AND COINS, TABLES FOR THE DETERMINATION OF MINERALS, . INDEX, . • • • V

CHAP. VIII. — CATALOGUE OF AMERICAN LOCALITIES OF MINERALS, 358

377 382 384

388 415

GLOSSARY AND INDEX OF TERMS.*

ACICTILAR, [Lat. acusy a needle,] 53.

Adamantine, 56.

Adit. [Lat. aditus, an entrance.] The horizontal entrance to a mine.

Alkali. An oxyd having an acrid taste, and caustic ; as potash, soda.

Alkaline. Like an alkali.

Alliaceous, [Lat. allium, garlic,] 66.

Alloy. A mixture of different met' als (excluding mercury) by fusion together. Also, the metal used to deteriorate another metal by mixture with it.

Alluvial. [Lat. alluo, to wash over.] Of river or fresh-water origin.

Amalgam. [Gr. malagma, a softened substance.] A compound of mercury and another metal.

Amalgamation, 326.

Amorphous, [Gr. a, not, and morphe, shape,] 54.

Amygdaloidal, 339.

Anhydrous. [Lat. a, not, and hudor, water.] Containing no water.

Arborescent. [Lat. arbor, tree.] Branching like a tree.

Arenaceous. [Lat. arena, sand.] Consisting of, or having the gritty nature of, sand.

Argentiferous. [Lat. argentum, silver.] Containing silver.

Argillaceous. [Lat. argilla, clay.] Like clay ; containing clay.

Arsenical odor, 66.

Asparagus green. Pale green, with much yellow.

Assay. [Same etymology as essay.] To test ores by chemical or blowpipe examination ; said to be in the dry way, when done by means of heat, (as in a crucible,) and in the wet way, when by means of acids and liquid tests.

Assay. The material under chemical or blowpipe examination.

Astringent, 66.

Asteriated. [Gr. aster, star.] Having the appearance of a star within.

Augitic. Containing augite.

Auriferous. [Lat. aurum, gold.) Containing gold.

Axes, 24 ; of double refraction, 59.

Basaltic, 339.

Bath stone . A species of limestone ; called also Bath oolite ; named from the locality, in England.

Bevelment, beveled, 35.

Bitter, 66.

Bittern, 106.

Bituminous. Containing bitumen ; like bitumen.

Bladed. Thin blade-like.

Blast furnace, 233.

Blowpipe, 67 ; tests, 69, 70 : implements, 68, 69.

Blue-John. Name for fluor spar, used in Derbyshire, where it often has a bluish-purple color.

Botryoidal, [(?r. botrus, a bunch of grapes,] 53.

Boulder, bowlder. Loose rounded mass of stone.

Breccia.

Brittle, 53, 65.

Calcine. [Lat. calx, burnt limestone.] To heat, in order to drive off volatile ingredients, and make easy to be broken or pounded.

Calcination. The process of calcining. -. ,

Carat, 82.

Carbon. Pure charcoal.

Carbonate. A salt containing carbonic acid. Carbonated ; containing carbonic acid, as carbonated springs.

* The number after a word signifies the page where it is explained. The etymology is given in brackets, wherever it was deemed important.

Vlll

GLOSSARY AND INEEX OP TERMS.

Carbonize. To convert into charcoal.

Carburet. A compound of an element with carbon, not acid.

Catalan forge, 237.

Celandine green. Green with blue and gray ; from the plant called celandine.

Cementation, 238.

Chalybeate. Impregnated with iron, 80.

Chert. A siliceous stone containing some lime ; also, hornstone.

Chlorid. Combination of an element with chlorine.

Chloritic. Containing chlorite.

Chromate. A salt containing chromic acid.

Cinereous. [Lat. cinis, ashes.] Resembling ashes.

Cleavage 33.

Coke, 90.

Columnar, 52.

Compound crystals, 42.

Conchoidal, 65.

Coralloidal. Having a resemblance to coral.

Cretaceous. [Lat. creta, chalk.] Pertaining to chalk.

Cropping out. The rising of layers of rock to the surface.

Crucible. [Lat. crux, a cross.] A pot made of earth or clay for melting, or reduction.

Cruciform, [Lat. crux, a cross,] 43.

Crystal, [Greek krustallos, ice,] 19 ; systems of crystallization, 24, 32.

Cube, 25.

Cupel, cupellation, 317, 328.

Cupreous. [Lat. cuprum, copper.] Containing copper.

Curved crystals, 42.

Decrepitate. To crackle and fly apart when heated.

Deflagrate. To burn with vivid combustion.

Deliquesce. To change to a liquid, on exposure ; arising from the attraction of moisture.

Dendrites. [Gr. dendron, tree.]

Delicate delineations branching like a tree ; due to infiltration of oxyd of iron or manganese.

Density. Specific gravity.

Desiccate. To dry, to exhaust of moisture.

Diaphaneity, 58*

Dichroism, 57.

Dimetric system, 32.

Dimorphism, 44.

Divergent, 53.

Disintegrate. To fall to pieces ; a result of exposure and partial decomposition.

Disseminated. Scattered through a rock or gangue.

Dodecahedron, rhombic, 25 ; isosceles, 39, fig. 65 ; pentagona!37 ; scalene, 40.

Dolomitic. Pertaining to dolomite.

Dressing of ores. The picking and sorting of ores, and washing pre* paratory to reduction.

Drusy, 54.

Dull, 56.

Earthy. Soft like earth, and with* out luster.

Ebullition. The state of boiling.

Effervescence, 67.

Effloresce. To change to a state of powder, by exposure ; arises from the escape of water.

Elastic, 53, 65. Electricity of minerals, etc., 62.

Elements, 72.

Ellipsoid, 42.

Elutriation. [Lat. elutrio, to pour from one vessel to another.] Mixing a powdered substance (as powdered flint) with water, and then after the coarser particles have subsided, carefully decanting the liquid and putting it away to settle, in order to obtain the impalpable powder which is finally deposited.

Elvan. In Cornwall, the granite masses forming broad veins in the killas, and containing the stockwerks.

Enamel. A glass having an ap-

GLOSSARY AND INDEX OF TERMS.

IX pearance like porcelain, or like

the surface of a tooth.

Evaporate. To become a vapor ;

to cause to become a vapor.

Even fracture, 65.

Exfoliate. To separate into thin

leaves, or to scale off.

Fault. Dislocation along a fissure, as often in coal beds, 87.

Feldspathic. Containing feldspar as a principal ingredient ; consisting of feldspar.

Ferruginous. [Lat. ferrum, iron.] Containing iron.

Fetid, 66.

Fibrous, 52.

Filament. A thread-like fiber.

Finery furnace. A furnace used in the conversion of cast iron into bar iron.

Filiform, [Lat.filum, a thread,] 53.

Flexible, 53, 65.

Fluate. Containing fluoric acid.

Flux, [Lat. fluo, to flow,] 69.

Foliaceous, 53.

Forceps, Platinum, 69.

Fracture of minerals, 65.

Friable. Easily crumbling in the fingers.

Fundamental forms, 23.

Furnace, blast, 233 ; reverberatory, 327 ; Catalan, 237.

Gallery. A horizontal passage in mining.

Gangue, 204.

Gelatinize, 67.

Geniculate. [Lat. genu, knee.] Bent at an angle, 43.

Geode. [Gr. gceodes, earth-like.] A cavity studded around with crystals or mineral matter, or a rounded stone containing such a cavity.

Glance. [Germ, glanz, luster.] Certain lustrous metallic sulphurets of dark shades of color.

Glimmering. Glistening, 56.

Globular, 53.

Goniometer, common, 47 ; reflecting, 50.

Granular. Consisting of grains.

Granulate ; to reduce to grains.

Hackly, 65.

Hardness, scale of, 64.

Hemihedral forms, 37.

Hepatic. [Gr. hepar, liver.] Having an external resemblance to liver.

Hexagonal prism, 27.

Hexagonal system, 33.

Homogeneous. Of the same texture and nature throughout.

Hyacinth red. Red with yellow and some brown.

Hyaline. [Gr. hualos, glass.] Resembling glass in transparency and luster.

Hydrated. [Gr. hudor, water.] Containing water.

Ignition. [Lat. ignis, fire.] The state of being so heated as to give out light ; at a red or white heat.

Impalpable, 53.

Implanted crystals. Attached by one extremity.

Incandescence. White heat.

Incrustation. A coating of mineral matter.

Indurated. Hardened or solidified.

Infiltrate. To enter gradually, as water, through pores.

Infusible. In mineralogy, not fusible by means of the simple blowpipe.

Inspissate. To thicken.

Intumesce. To froth.

Investing. Coating or covering, as when one mineral forms a coating on another.

Irised. [Lat. iris, rainbow.] Having the colors of the spectrum.

Iridescence, 57.

Isomorphism, isomorphous, 74.

Juxtapose. To place contiguous.

Killas. In Cornwall, the schistose rock in which the lodes occur.

Lamellar, 53.

GLOSSARY AND INDEX OF TERMS.

Lapidification. [Lat. lapis, a stone.] The process of changing to stone.

Lapilla. Small volcanic cinders.

Lavender-blue. Blue with some red and much gray.

Leek-green. The color of the leaves of garlic.

Lenticular. Thin, with acute edges something like a lens, except that the surface is not curved.

Leucitic. Containing leucite.

Levigation. [Lat. levis, light.] The process of reducing to a fine powder.

Liquation. [Lat. liquo, to melt ] The slow fusion of an alloy, by which the more fusible flows out and leaves the rest behind, 328.

Lithographic stone. A compact grayish or yellowish-gray limestone of very even texture and conchoidal fracture ; used in lithography. That of Solenhofen, near Munich, is most noted.

Lithology. [Gr. lithos, stone, and logos, a discourse.] Mineralogy.

Lixiviate. [Lat. lixivium, lye.] To form a lye, by allowing water to stand upon earthy or alkaline material, and draining it off below, after it has dissolved the soluble ingredients present.

Lode. [Sax. losdan, to lead.] In mining, a vein of mineral substance ; usually a vein of metallic ore. The lode is said to be dead when the material affords no metal.

Lodestone, 217.

Made. A compound crystal, or one having a tesselated structure.

Magnesian. Containing magnesia.

Magnetism of minerals, 63.

Malleable, [Lat. malleus, a hammer,] 65.

Mammillary, [Lat. mammilla, a little teat,] 53.

Manganesian. Containing manganese.

Marly. Having the nature of marl containing marl.

Massive. Compact, and having no regular form.

Matrix. [Lat. matrix, from mater, mother.] The rock or earthy material, containing a mineral or metallic ore.

Metallic, 55, 56. Metallic-pearly, 55. Metallic-adamantine, 56.

Metalliferous. Yielding metal.

Metallurgy. [Gr. metallon, and ergon, work.] The science of the reduction of ores.

Micaceous, 53.

Mineralized. Changed to mineral by impregnation with mineral matter. Also being disguised in character by combination with other substances ; thus used with regard to metals when in combination with sulphur, arsenic, carbonic acid, or anything that affects their malleability and other qualities.

Molecules, 42.

Molybdate. A salt containing molybdic acid.

Monoclinate, 33.

Monometric, 32.

Mountain limestone. A limestone of the lower part of the coal series ; called also carboniferous limestone.

Muffle, 317.

Nacreous. Like pearl.

Native metal, 202.

Nitrate. A salt containing nitric acid.

Nitriary, 102.

Nucleus. The center particle or mass around which matter is aggregated.

Ochreous. Like ocher.

Octahedron, pp. 23, 25, 26.

Octahedral. Having the form of an

octahedron.

Odor of minerals, p. 66.

Oolite. [Gr. oon, egg,] p. 349.

Opalescence, p. 57.

Opaline. Like opal.

Opalized. Changed to opal.

GLOSSARY AND IltfDEX OF TERMS.

XI

Opaque, p. 58.

Ore, 202. Also; by miners, a disseminated ore and the including stone together ; the term metal is often used for the pure ore.

Oxyd, 73.

Oxydizable. Capable of combining with oxygen.

Oxydating flame, 68.

Pearly 55.

Percolate. To pass gradually through pores.

Phosphorescence, 61.

Pisolitic, [Lat. pisum, a pea,] composed of large round grains or kernels, of the size of peas.

Pistachio-green. Green with yellow, and some brown.

Plastic. Adhesive, and capable of being moulded in the hands.

Plumose. Having the shape of a plume, or feather.

Polarisation, 60.

Polarity, 62.

Polychroism, 57.

Play of colors, 57.

Plutonic rocks. Granite and allied crystalline rocks.

Polyhedral. [Gr. polus, many, and hedraface.) Having many sides.

Polymorphism, 44.

Porous. Having minute vacuities, visible or invisible to the naked eye ; a loose texture, allowing Water to filtrate through.

Pdrphyritic. Like porphyry, 340.

Prisms, 23.

Pseudomorphous, 54.

Puddling Furnace. A reverberatory furnace, used in converting cast into bar iron, after the finery furnace.

Pulverize. [Lat. pulvis, dust,] to reduce to powder.

Pulverulent. Like a fine powder slightly compacted.

Pyritous. Having the nature of pyrites, 212.

Pyro-electric, 62.

Quartationj 318.

Quartzose. Containing quartz as a principal ingredient.

Radiated, 53.

Rake -vein. A perpendicular mineral fissure.

Rectangle, 24.

Reduction of ores, 204.

Reduction flame, 68.

Refraction, 58.

Refractory. Resisting the action of heat ; infusible.

Refrigerate. To cool.

Regulus. The pure state of a metal, as regulus of antimony.

Reniform. [Lat. ren, kidney,] 53.

Replacement, 35. Resinous, 55.

Resplendent. Having a brilliant luster.

Reticulated. [Lat. rete, a net,] 52, 54.

Reverberatory furnace, 327.

Rhombohedron, 27.

Riddling or sifting of ores. Putting the broken or pulverized ore in a seive, and plunging the seive into water, by which, the whole powdered material is raised by the water and the metallic part sinking first, may be separated to a great extent from the rest.

Roasting. Exposing to heat hi piles, or in a furnace, and thus driving offany volatile ingredient.

Saccharoid. [Gr. sakchar, sugar.] Having a texture like loaf sugar.

Saline, (Lat. sal, salt.) Salt like ; cojitaining common salt.

Salt. In chemistry, any combination of an acid with a base, 74.

Scale of hardness, 64.

Schlich. The finely pulverized orfe and gangue.

Schistose. Having a slaty structure.

Scopiform, (Lat. scopa, a broom.) Like a broom in form.

Scoria, (L. scoria, dross,) 205, 341.

Secondary forms, 34. Sectile, 65.

Semitransparent, 58.

Shaft. A vertical or much inclined pit, cylindrical in form.

xii

GLOSSARY ANt> INDEX OF TERMS.

Shale, 341. Shining, 56.

Silicate, 74.

Siliceous. Consisting of, or containing silex, or quartz.

Silky, 56.

Silurian. A term applied to the fossiliferous rocks, older than the coal series.

Smelting of iron ores, 233.

Spathic, (Germ, spath.'} Like spar.

Spar. Any earthy mineral having a distinct cleavable structure and 'some luster, as calcareous spar.

Stalactitic, (Gr. stalazo, to drop or distil,) 54, 116.

Stalagmite, 116.

Specific gravity, 63.

Splendent, 56.

Splintery. Having splinters on a surface of fracture.

Stamping. Reducing to coarse fragments in a stamping mill.

Stellated, (Lat. Stella, star,) 52.

Strata. A series of beds of rock.

Streak, streak -powder, 56.

Striated. Lined or marked with parallel grooves, more or less regular.

Stockwerks. In Cornwall, works in beds and veins of ore. The works in alluvial deposits are distinguished as stream-works.

Sub. In composition, signifies beneath ; also, somewhat, or imperfectly, as submetallic, means imperfectly metallic.

Sublimation, (Lat. sublimis, high.) Rising in vapor, by heat, to be again condensed. •

Submetallic, 55.

Subtranslucent, 58.

Subtransparent, 58.

Subterbrand. A name given to Bovey coal, or brown coal.

Subvitreous, 55.

Sulphate. A salt containing sulphuric acid.

Sulphureous, 66.

Sulphuret. Combination of a metal with sulphur.

Tarnish, 57.

Tertiary strata. Strata more re* cent in age than the chalk, and antecedent to the recent epoch.

Tesseral system, (Lat. tessera, a four square tile, or dice,) 32.

Tetrahedron, (Gr. tetra, four, hedra, face,) 37.

Titaniferous. Containing titanium.

Transition rocks. The older silurian, which were formerly supposed to contain no trace of fossils.

Translucent, 58.

Transparent, 58.

Triclinate, 33.

Trimetric, 33.

Trimorphism, 44.

Truncation, truncated, 35.

Tufaceous. Like tufa, 347.

Tuyeres, or twiers, 234.

Twin crystals, 42.

Unctuous. Adhesive, like grease.

Ustulation. [L. ustulatus} scorched, or partly burnt.] Roasting of ores.

Veins. In miner's use, small lodes.

In geology, any seams of rock material, intersecting strata crosswise.

Vein-stone. The gangue of a metal or mineral.

Verdigris-green. Green inclining to blue ; the color of verdigris.

Vesicular. Containing small vacuities.

Viscous, 65.

Vitreous, (Lat. vitrum, glass,) 55.

Vitrification. Conversion to glass.

Volatile. Capable of passing easily to a state of vapor.

Washing of ores. Exposing them after stamping, (or before if in fragments,) to running water, which carries off the earthy material, it being lighter than the

Zeolitic. Having the nature of a zeolite, 163.

MINERALOGY.

Chapter I. General Characteristics Of Minerals

Relations of the three Kingdoms of Nature. Viewing the world around us, we observe that it consists of rocks, earth or soil, and water ; that it is covered with a large variety of plants, and tenanted by myriads of animals. These three familiar facts lie at the basis of three primary branches of knowledge. The animals, of whatever kind, from the animalcule to man, give origin to that branch of science which is called Zoology; the various plants, to the science of Botany ; and the rocks or minerals, to Mineralogy. The first two of these departments embrace all natural objects that have life, and treat of their kinds, their varities of structure, their habits, and relations.

The third branch of knowledge, Mineralogy, relates to inanimate nature. It describes the kinds of mineral material forming the surface of our planet, points out the various methods of distinguishing minerals, makes known their uses, and explains their modes of occurrence in the earth.

Importance of the Science of Mineralogy. To the unpracticed eye, the costly gem, as it is found in the rocks, often seems but a rude bit of stone ; and the most valuable ores may appear worthless, for the metals are generally so disguised that nothing of their real nature is seen. There is an ore of lead which has nearly the color and luster of Glauber salt ; an ore of iron that looks like sparry limestone ; an ore of silver that might be taken for lead ore, and another that resembles wax. These are common cases, and

What classes of natural objects exist 1 Of what does Zoology treat 1 What Botany ? Of what does Mineralogy treat 1 What advantages result from the study of minerals ? 2 consequently much careful attention is required of the student to make progress in the science. Moreover, a great proportion of the mineral species are of no special value, and they occur under so many forms and colors that close study is absolutely necessary in order to be able to distinguish the useless, and avoid being deceived by them ; for such deceptions are common and often lead to disastrous consequences in mining.

The science of Mineralogy is, therefore, eminently practical. Moreover, the very existence of many of the arts of civilized life, depends upon the materials which the rocks afford. Besides the metals and metallic ores, we here find the ingredients for many common pigments, and for various preparations used in medicine ; also the enduring material so valuable for buildings and numberless other purposes : moreover, from the rocks comes the soil upon which we are dependent for food. At the same time, the student of Mineralogy who is interested in observing the impress of Infinite wisdom in nature around him, finds abundant pleasure in examining the forms and varieties of structure which minerals assume, and in tracing out the principles or laws which Creative power has established even throughout lifeless matter, giving it an organization, though simple, no less perfect than that characterizing animate beings.

What is a Mineral ? It has been remarked that Mineralogy, the third branch of Natural History, embraces every thing in nature that has not life. Is, then, every different thing not resulting from life, a mineral 1 Are earth, clay, and all stones, minerals ? Is water a mineral ?

All the materials here alluded to properly belong to the mineral kingdom. The minute grains which make up a bank of clay or earth, are all minerals, and if their characters could be accurately ascertained, each might be referred to some mineral species. It is evident, however, that the clay itself, unless the grains are all of one kind, is not a distinct species, though mineral in composition : it is a compound mass or an aggregate of different mineral grains ; and this is true of all ordinary soil and earth. In the same manner very many rocks are aggregates of two or more minerals in intimate union. Mineralogy distinguishes the species, and enables us to point out the ingredients which are mixed in the constitution of such rocks. It searches for specimens that

Is clay a mineral? What is the nature of many rocks 1 are pure and undisguised, ascertains their qualities and their varieties, and thus prepares the mind to recognize them under whatever circumstances they may occur.

Water lias no qualities which should separate it from the mineral kingdom. All bodies have their temperature of fusion ; lead melts at 612° F. ; sulphur at 226° F. ; water at 32° ; mercury at — 39°. No difference therefore of this kind can limit the mineral kingdom. Ice is as properly a rock as limestone ; and were the temperature of our globe but a little lower than it is, we should rarely see water except in solid crystal-like masses or layers. Our atmosphere, and all gases occurring in nature, belong for the same reason to the mineral kingdom. Several of the gases have been solidified, and we can not doubt that at some specific temperature each might be made solid. We can not, therefore, exclude any substance from the class of minerals because at the ordinary temperature it is a gas or liquid. Quicksilver with such a rule would be excluded as well as water.

A mineral, then, is any substance in nature not organized by vitality, and having a homogeneous structure. Thejirst limitation here stated — not organized by vitality — excludes all living structures, or such as have resulted from vital powers ; and the second — a homogeneous structure— excludes all mixtures or aggregates. The different spars, gems, and ores are minerals, while granite rock, slate, clay and the like, are mineral aggregates. This compound character is apparent to the eye in granite, for there is no difficulty in picking out from the mass a shining scaly mineral, (mica,) and with more attention, semi-opaque whitish or reddish particles (feldspar) will be easily distinguished from others (quartz) that have a glassy appearance.

It is a popular belief, that stones grow. Yet the absence of any proper growth is the main point distinguishing minerals from objects that have life. Plants and animals are nourished by the circulation of a fluid through their interior ; in plants, we call the fluid sap ; in animals, blood ; and increase or growth takes place by means of material secreted from this circulating fluid. The living being commences with the mere germ, and grows through youth to maturity ;

Why should water and gases rank with minerals. What is a mineral ? What limitations are here implied 1 What is the nature of granite 1 and when this fluid finally ceases to circulate, it dies and soon decays.

Minerals, on the contrary, have no such nourishing fluid. The smallest particle is as ..perfect as the mountain mass. They increase in size only by additions to the surface from some external source. The deposit of salt forming in an evaporating brine, has layer after layer of particles added to it, and by this mode of accumulation, its thickness is attained.

Beds of an ore of iron, called bog iron-ore, are sometimes said to grow. They do in fact increase in extent. Rills of water running from the hills wash out the iron in the rocks they pass over, decomposing and altering the condition of the ore, and cany it to low marshy grounds. Here the water becomes stagnant, and gradually the iron is deposited. This bog ore, as the name implies, is found mostly in low marshy places, and often contains nuts, leaves, and sticks, changed to iron ore. The increase here is obviously by external additions.

In limestone caverns, and about certain lakes and streams, the water contains much carbonate of lime. As it evaporates, layer after layer of the lime is deposited, till thick beds are sometimes formed. In caverns, the water comes dripping through the roof, dropjjy drop, and each drop as it dries, deposits a little carbonate of lime. At first it forms but a mere wart on the surface ; but it gradually lengthens, till it becomes a long tapering cylinder, and sometimes the pendant cylinder, or stalactite, as it is called, reaches the floor of the cave, and forms a column several feet in diameter.

It thus appears that minerals increase, or enlarge, by accretion, or additions to the surface only. They decrease, or the surface is worn away, by the action of running water and other agents. When they decay, as sometimes happens from contact with air and moisture, or some other cause, the change begins with the surface, and results in producing one or more different minerals. The line of demarkation, therefore, between living beings, and minerals or inorganic matter, is strongly drawn.

Characters of Minerals. In pursuing the subject of min-

What are the different modes of increase in the animate and mineral kingdoms? Mention examples of increase in mineral substances, and explain the mode.

erals, there are various qualities presented for our study. We observe that stones or minerals have color ; they have hardness in different degrees, from being soft and impressible by the nail, to the extreme hardness of the diamond ; they have weight ; they have luster, from almost a total absence of the power of reflecting light to the brilliancy of a mirror. Some are as transparent as glass and others are opaque. A few have taste. These are the most obvious characters, and characters to which the mind would at once appeal in distinguishing species.

Other characters of equal importance are found in the internal and external structure of minerals. On examining a piece of coarse granite, we find that each scale of mica may be split by the point of a knife into thinner leaves. Here is evidence of a peculiar structure, called cleavage; and wherever mica is found, this peculiarity is constant. The feldspar in the same rock, if examined with care, will be found to break in certain directions with a smooth, or nearly smooth plain surface, showing a luster approaching that of glass, though somewhat pearly. It is true of feldspar also, that this cleavage is a constant character for the species, as regards direction and facility. In nearly all minerals, this kind of structure, more or less perfect in quality, may be distinguished. In a broken bar of iron the irregularity of the grains proceeds from this cause. In granular marble, although the mass as a whole has no such structure, the several grains if attentively examined will be seen to present a distinct cleavage structure and consequent angular forms. In finer varieties, the grains may be so small that the characters cannot be observed ; or again the texture of the mass may be so compact that not even grains can be distinguished.

This cleavage, then, is a peculiarity of internal structure. It is intimately connected with another fact, — that these same minerals often occur under the form of some regular solid with neat plane surfaces ; and are finished with a symmetry and perfection which art would fail to imitate. These forms are their natural forms, and every mineral has its own distinct system of forms. The beauty of a cabinet of minerals arises to a great extent from the variety of forms and

What physical characters are to be observed in the study of minerals? What character depends on internal structure1? Mention examples and explain. What other character depends on structure ? 2* high finish of these gems of nature's workmanship. The mineral quartz sometimes occurs in crystals consisting of two pyramids united by a short six-sided prism, and they have generally the transparency and almost the brilliancy of the diamond, whose name they bear in common language. The " diamonds" of central New York, and many other localities, are of this kind. In other cases a large surface of rock sparkles with a splendid grouping of the pyramidal glassy crystals. We might draw other illustrations from almost all the mineral species. But this will suffice to show that in addition to the physical characters above mentioned, there are others dependent on structure, which afford distinctions of species, apparent both in external form and internal cleavage.

Still other characters are derived from subjecting species to the action of heat, and to acids or other re -agents. One mineral, when heated, melts ; another is infusible, or fuses only on the edges ; another evaporates. By such trials, and others hereafter to be described, we study minerals in a different way, and ascertain their chemical characters. This mode of investigation more minutely pursued, leads to a knowledge of the constitution of minerals, a branch of study which belongs properly to Analytical Chemistry : the results are of the highest importance to the mineralogist.

It is perceived, therefore, that the learner may (1) examine into the peculiarities of structure among minerals ; (2) he may attend to the physical characters depending on light, hardness, and gravity ; (3) he may acquaint himself with the effects of heat and chemical re-agents — the chemical characters. These are three sources of distinctions giving mutual aid, and a knowledge of all is necessary to the mineralogist. To learn to distinguish minerals by their color, weight, and luster, is so far very well ; but the accomplishment is of a low degree of merit, and when most perfect, makes but a poor mineralogist. But when the science is viewed in the light of Chemistry and Crystallography, it becomes a branch of knowledge, perfect in itself, and surprisingly beautiful in its exhibitions of truth. We are no longer dealing with pebbles of pretty shapes and tints, but with objects modeled by a Divine hand ; and eveiy additional fact becomes to the mind a new revelation of His wisdom.

Mention examples. What other characters are there ? Enumerate the kinds of characters presented by minerals,

CRYSTALLOGRAPHY. 19

In the study of this science, the learner will be introduced first to the structure of minerals. The subject is treated of under its usual name, crystallography.