Document rBOqvKqKVw7bV601bo1pEar2V

FILE NAME Talc TALC DATE 1998 DOC TALC110 DOCUMENT DESCRIPTION Book Excerpt - Mineralogy Textbook - Talc oe, ore - Lo sew Pu oo "| THE NEW YORK _ _ PUBLIC LIBRARY c Sf" ASTOR LENOX AND |, .. TILDEN FOUNDATIOFOUNNDASTIONS 11 A BOOK OF MINERALOGY WITH AN EXTENDED TREATISE ON CRYSTALLOGRAPHY AND PHYSICAL MINERALOGY BY EDWARD SALISBURYDANA Professor of Physics and Curator Yale University ofMinera logy Mineralogy NEW EDITION ENTIRELY REWRITTEN AND ENLARGED With nearly 1000 Figures and a Colored Plate NEW YORK JOHN WILEY & SONS LONDON CHAPMAN & HALL wom ~., hlin a LIMITED THE NEW YORK PUBLIC LIBRARY 589378 ASTOR LENOX AND TILDEN FOUNDATIONS R 1913 L Copyright 1898 , oe - eel s BY . aa EDWARD S. DAN~ * eee 2 SILICATES 479 Deweylite A marnesian silicate near serpentine but with more water Formula perhaps 4MgO 3SiO2.6H OAmorphous resembling gum arabic or a resin H. = 28.5 G. = 20-22 Color whitish yellowish reddish brownish Occurs with serpentine in the Fle.msthal Tyrol also at Texas Penn and the Bare Hils Md Gymnite of Thomson namednamed from youros naked in allusion to the locality at Bare Hills Md is the same species Genthite Nickel Gymnite A gymuite with part of the magnesium replaced by nickel 2NiO.2MgO.8SiO Amorphous with a delicate stalactitic surface incrusting H. 3-4 sometimes very soft G. 2.409 Luster res n10118 Color ale applegreen or yellowish From Texas Lancaster Co. Pa in thin crusts on chromite Garnierite Noumeite Au important ore of nickel consisting essentially of a hydrated silicate of magnesium and nickel perhaps S.O + aq but very variable in com- Mg position particularly as regards the nickel and magnesium not always homogeneous Amorphous Soft and friable G. = 2.8-2.8 Luster dull Color bright green pale green to nearly white lu part unctuous sometimes adheres to the tongue Occurs in serpentine rock near Noumea capital of New Caledonia associated with chromic iron and steatite where it is extensively mined A similar ore occurs at Riddle in Douglas County southern Oregon also at Webster Jackson Co. N. C. TALO Orthorhombic or monoclinic Rarely in tabular crystals hexagonal or rhombic with prismatic angle of 60 Usually foliated massive sometimes in globular and stellated groups also granular massive coarse or fine fibrous pseudomorphous Cleavage basal cryptocrystaline also compact or perfect Sectile cFrlyepxtiobclreysitnaltlihnien lamin^but not elastic Percussion a rayed star oriented as with the micas H. = 1-1.5 G. = 2.7-2.8 Luster pearly on cleavage surface Feel greasy Color apple- green to white or silvery also greenish gray and dark green sometimes bright green perpendicular to cleavage surface and brown and less translucent at right angles to this direction brownish to blackish green and reddish when impure Streak usually white of dark green varieties lighter than the color Subtransparent to translucent Optically negative Axial angle small y ---- = 0.035-0.050 Ax pl a Bx 1 ordinarily Soapstone greenish Foliated Tale and presenting Consists of folia usually easily separated having a greasy feel green white and white colors G = 25-2-78 255-2-78 Massive Stentite or Soapstone Speckstein Germ a Coarse granular grayish green and brownish gray in color H. = 1-2.5 alone is ordinary soapstone more or less impure b Fine granular or cryptocrystalline and soft enough to be used as chalk as the French chalk which is white with a pearly luster slaty talc harder than ordinary tale c Induruted tale An impure Pseudomorphous a Fibrons fine to coarse altered from enstatite and tremolite b Rensselaerite having the form of pyroxene from northern New York and Canada Comp Anacid metasilicate of magnesium or O.3MgO.4SiO = Silica 63.5 magnesia 317 water 4.8 = 100. The water goes off only at a red heat Nickel is sometimes present in small amount Pyr etc. the closed tube B B. when intensely ignited most varieties yield water In the platinum forceps whitens exfoliates and fuses with difficulty on the thin edges to white enamel Moistened with cobalt solution assumes on ignition a pale red color Not decomposed by acids Rensselaerite is decomposed by concentrated sulphuric acid Diff pearly Characterized by extreme softness soapy feel common foliated structure Juster it is flexible but inelastic Yields water only on intense ignition Tale or steatite is very common mineral and in the latter form constitutes extensive beds in some regions It often associated with serpentine talcose or chloritic schist and dolomite and frequently contains crystals of dolomite breusmerite also asbestus actinolite tourmaline inagnetite Steatite is the material of many pseudomorphs among which the most common are those after pyroxene hornblende mica scapolite and spinel The magnesian minerals are * 480 DESCRIPTIVE MINERALOGY those those which commonly afford steatite by alteration while like scapolite nephelite which contain soda and no magnesia most frequently yield pinite pseudomorphs There are also steatitic pseudomorphs after quartz dolomite topaz chiastolite staurolite cyanite garnet vesuvianite chrysolite gehlenite Talc in the fibrous form is pseudomorph after enstatite and tremolite Gothard Apple talc occurs at Mt. Greiner in the Zillerthal Tyrol in the Valais and St. in Switzerland in Cornwall near Lizard Point with serpentine the Shetland islands In N. America foliated talc occurs in Maine at Dexter In Vermont at Bridgewater handsome green talc with dolomite Newfane In Mass at Middlefield Windsor Blan ford Andover and Chester In R. Island at Smithfield delicate green and white in a crystalline limestone In N. York at Edwards St. Lawrence Co. a fiue fibrous talc Unionville agalite associated with pink tremolite on Staten Island In N. Jersey Sparta In Penn at Texas Nottingham in South Mountain ten miles south of Carlisle at Chestnut Hill on the Schuylkill talc and also soapstone the latter quarried extensively In Maryland at Cooptown of green blue and rose colors In N. Car at Webster Jack- son Co. In Canada in the townships Bolton Sutton and Potton Quebec with steatite in beds of Cambrian age in the township of Elzevir Hastings Co. Ontario an impure grayish var in Arch^anrocks ra SEPIOLITE Meerschaum Germ L'^ cumede mer Fr. Compact with a smooth feel and fine earthy rarely fibrous H. = 2-2.5 G. 2. Impressible floats on water Color grayish white white or reddish tinge bluish green Opaque texture or like also by the nail In dry masses with a faint yellowish or Comp.-H.Mg or O.2MgO.3SiO = Silica 60.8 magnesia 27 water 12.1 = 100. Some analyses show more water 2H which is probably to be regarded as hygroscopic Copper and nickel may replace part of the magnesium Pyr etc. the closed tube temperature gives much water and a bygroscopic yields first burnt smell B.B. some moisture and at a higher varieties blacken then burn white and fuse with difficulty on the thin edges With cobalt solution a pink color on ignition Decomposed by hydrochloric acid with gelatinization Occurs in Asia Minor in masses in stratified earthy or alluvial deposits at the plains of Eskihi sher at Hrubechitz in Moravia in Morocco called in French Pierre de Savon de Maroc at Vallecas in Spain in extensive beds fibrous mineral having the composition of sepiolite occurs in Utah The word meerschaum is German for froth and alludes to its and color lightness Sepiolite Glocker is from ^niacuttle the bone of which is and porous and being light also a production of the sea " deinde spumam marinam siguificabat says Glocker Connarite A hydrous nickel silicate perhaps H.Ni In small fragile grains G. = 2.459-2-619 ~ oloryellowish greeu From R^ttisin Saxon Voigtland Spadaite Perhaps Capo di Bove near 5MgO 6810 Rome Massive amorphous Color reddish From SAPONITE Plotine Massive In nodules or filling cavities Soft like butter or cheese but brittle on drying G. - 2.24-2.30 Luster greasy Color white yellowish grayish green bluish reddish Does not adhere to the tongue impure Comp hydrous silicate of magnesium and aluminium but the material is amorphous and probably always and hence analyses give no uniform results Contains SiO 40-45 p c AI 5-10 p MgO 19-26 p c H 19- 21 .; also Fe FeO etc. Pyr etc.-B.B. gives out water very readily and blackens thin splinters fuse with difficulty on the edge Decomposed by sulphuric acid Obs Occurs in cavities in basalt diabase etc also with serpentine Thus at Lizard Point Cornwall in veins in serpentine at various localities in Scotland etc.