| dc.description.transcription | Vol. 12 November, 1927 No. 11 The American Mineralogist Journal of the Mineralogical Society of America EDITOR WALTER F. HUNT ASSOCIATE EDITORSWILLIAM F. FOSHAG, SAMUEL G. GORDON, ESPER S. LARSEN, JOHN I. LONSDALE, E. POITEVIN AND AUSTIN F. ROGERS CONTENTS The nomenclature of silica. Gilbert Hart 383 Barytocelestite from the Kingden Lead Mines, Galetta, Ontario E. L. Bruce and Margaret Light 396 The Florence Meteorite of Williamson Co., Texas. John T. Lonsdale 308 A reexamination of the lead sulphosalt keeleyite from Bolivia Earl V. Shannon and M. N. Short 405 Apatite crystals from Want's Quarry, near Pilot, Maryland Earl V. Shannon 408 On the determination of alkalies in rocks and minerals. Earl V. Shannon 411 Notes and news: Studies in the mica group (a discussion). A. F. Hallimond 413 Garnets in the Navajo country. Albert B. Reagan 414 Proceedings of Societies: Philadelphia Mineralogical Society. 416 Published monthly by the George Banta Publishing Company 450-454 Ahnaip St. Menasha, Wisconsin Single Copies 30c Annual subscription $3.00 Mineralogical Society of America Honorary President: Edward S. Dana, Yale University, New Haven, Conn. President: Austin F. Rogers, Stanford University, California. Vice President: George L. English, Rochester, New York. Secretary: Frank R. Van Horn, Case School of Applied Science, Cleveland, O. Treasurer: Alexander H. Phillips, Princeton University, Princeton, N. J. Editor: Walter F. Hunt, University of Michigan, Ann Arbor, Mich. Councilors: A. L. Parsons, University of Toronto, Toronto, Canada. William F. Foshag, U. S. National Museum, Washington, D. C. W. A. Tarr, University of Missouri, Columbia, Mo. Alexander N. Winchell, University of Wisconsin, Madison, Wisconsin. Waldemar T. Schaller, U. S. Geological Survey, Washington, D. C. The American Mineralogist Journal of the Mineralogical Society of America A journal containing articles on mineralogy, crystallography and allied sciences, issued about the 15th of every month. Contributions are invited from everyone. The general conduct of the journal is in the hands of the Editor, Walter F. Hunt, Ann Arbor, Michigan. The council of the Mineralogical Society has appointed the following board of associate editors, to whom should be sent articles dealing with the special subjects indicated: Esper S. Larsen, Harvard University, Cambridge, Mass., Optical crystallography. Samuel G. Gordon, Academy of Natural Sciences, Philadelphia, Pa., Eastern localities. Austin F. Rogers, Stanford University, California, Western localities. John T. Lonsdale, University of Texas, Southern localities. E. Poitevin, Ottawa, Canada, Canadian localities. William F. Foshag, U. S. National Museum, Washington, D. C., New minerals. Manuscripts submitted for publication in The AMERICAN MiNEraLOGIST should be clearly typewritten and in suitable form for printing. References should appear as footnotes and include year of publication. Contributors of leading articles are given without charge 25 copies of the issue containing their article. If additional reprints are desired these can be purchased (without covers), at the following rates: […] THE LEITZ WORKS ARE THE LARGEST MICROSCOPE MANUFACTURERS IN THE WORLD LEIT EST’D: 1849 THE STANDARD OF OPTICAL AND MECHANICAL PRECISION PETROGRAPHICAL [Polarizing] MICROSCOPES In Stock for Immediate Delivery The enlarged Tube accommodates oculars of wide diameter, whereby the field of view is increased 50% over other types of instruments. ELENZ, WETALAN MODEL "GM'' for advanced Laboratory work MODEL "KM" for routine Laboratory work
The Leitz Works, as one of the pioneers in the manufacture of Petrographical microscopes, offer seven different models of these microscopes and a large variety of accessories for same, to afford a selection for any and all individual requirements. Reliable results are possible only with a microscope of precision and selecting a Leitz Microscope offers the guarantee of possessing an equipment of utmost efficiency. Write for Catalog (E) III-B E. LEITZ, INc. 60 East 10th St., NEW YORK AGENTS Pacific Coast States: Sent free to all members and fellows of the Mineralogical Society of America. Price to non-members, $3.00 per year (30c per copy) Remittances should be sent to Professor Alexander H. Phillips, Princeton University, Princeton, New Jersey. […] THE AMERICAN MINERALOGIST JOURNAL OF THE MINERALOGICAL SOCIETY OF AMERICA Vol. 12 NOVEMBER, 1927 No. 11 THE NOMENCLATURE OF SILICA GILBERT HART, Birmingham, Alabama. In its many forms, silica has been used in all stages of civilization, from the ancient flints of the Stone Age to the modern silica laboratory ware. Because of its many uses, and of the many varied forms in which it occurs, silica has been called by more names than any other mineral. Many of the older names of flint are now so obsolete that repetition is needless, but many of the present-day names for quartz gems are unknown save to a few jewellers [jewelers]. Then, too, the exact research of the modern laboratory has shown several distinct crystallographic varieties of silica; some of which are closely connected with the temperatures experienced in their life-history. The many different names, and their different connotations, which are now in use for silica minerals, call for a classification and arrangement in a more ample, yet more concise manner than is to be found in the usual discussion of the varieties of silica. This article is written with the hope of making a scientific classification of these names, so that the use of the different terms will no longer be a cause for tedious searching for definitions. I. CRYSTALLOGRAPHIC VARIETIES These varieties are named in the order formed with descending temperatures. Recrystallization changes occur at the temperatures noted when ample time is allowed for the action, often in the laboratory only in the presence of catalysts. Besides the changes at these critical temperatures, there are probably similar changes from unstable forms towards quartz at atmospheric temperatures, especially after long time intervals. With fairly rapid cooling or heating intermediate forms may not occur in their stable zone, but a direct change from one to another without the intermediate product may take place. Most of the recrystallization changes noted are found to occur at both ascending and descending temperatures. (A) SILICA GLASS--amorphous, a true non-crystalline glass, stable below the melting point and above the "g" temperature. Quartz Glass, Fused Silica, Fused Quartz, are other names for this supercooled liquid. In most forms at atmospheric temperatures there are traces of cristobalite. (B) CRISTOBALITE- isometric, or pseudo-isometric, "g" range is at 1710° where cristobalite changes to glass as temperatures rise, or glass to cristobalite as they fall. Christobalite, an alternate spelling. Beta Cristobalite, also called High Cristobalite, is the high temperature product, forming in the "g" range in cooling. It is isometric, and in cooling recrystallizes to Alpha Cristobalite, or Low Cristobalite, at 200-275°, providing cooling through the "ct" and "g" ranges has been too rapid for recrystallization. It is tetragonal. (C) TRIDYMITE-hexagonal, bipyramidal. "ct" range is at 1470°, where cristobalite changes to tridymite on cooling. Glass may crystallize as tridymite at 1670° if the cooling was too rapid through the "g" range. Beta Second Tridymite, or Upper High Tridymite, is the high temperature product, forming in the "ct" range in cooling, and which recrystallizes to Beta First Tridymite, also called Lower High Tridymite, at 163° if cooling was too rapid for the "tq" transformation. This in turn alters to Alpha Tridymite, or Low Tridymite, at 117°, which is the usual tridymite of nature. Asmanite a meteoric tridymite, related to the above series. Vestan—a doubtful silica mineral, probably to be ascribed to tridymite. Granuline a doubtful pulverescent mineral which seems allied to tridymite on optical grounds. (D) QUARTZ- hexagonal, forms from tridymite in the "tq" range at 870° in cooling. Glass may change to crystalline quartz at about 1400° providing cooling was too rapid for the "g", "gt" and "ct" transformations. Beta Quartz, or High Quartz, is the high temperature product, forming at the "tq" point. It is hemihedral. On cooling it recrystallizes to Alpha Quartz, also called Low Quartz, at 573°, yielding the stable low temperature mineral. It is tetartohedral, showing polarity along the c axis and is divisable into Right Hand Quartz and Left Hand Quartz (E)?CHALCEDONY—a cryptocrystalline, or very finely fibrous mineral, which has not been successfully located in the thermal equilibrium diagram. Heating to 725-850° usually results in an alteration to tridymite, which thereafter acts as normal tridymite. Chalcedony is usually found as a deposit from solutions, and may be a mixture of glass and quartz, or more probably an intermediate product in the dehydration of the opal colloid. Various subdivisions of chalcedony have been made on optical grounds. Chalcedony biaxial, positive, elongation positive. Chalcedonite biaxial, negative. Lussatite biaxial, positive, parallel elongation. Quartzine-biaxial, positive, negative elongation. Pseudochalcedonite. Lutecite. Jenzschite differently soluble, but of same S. G. as chalcedony. Melanophlogite possibly impure chalcedony. Sulfuricin-probably a chalcedony rich in sulphur. (F) COLLOIDAL SILICA—is usually hydrous, and is commonly described under opal. II. PHENOCRYSTALLINE VARIETIES Both alpha and beta, right hand and left hand quartz are present in the varieties here considered. Rarely, perhaps, are included tridymites or cristobalites, but their occurrence is rare, and specimens are not often found under other than their type names. (A) CLEAR LARGE CRYSTALS, which may or may not have crystal faces, but are essentially large single individuals. (1) Colorless, transparent, lustrous. (a) Crystal—indicative of the clearness of ice. Mountain Crystal. Rock Crystal (b) "Diamond" indicative of the clearness of true diamond, and of the use as a substitute for diamond. Quartz "diamonds" are usually of local value only, though sometimes sold as imperfect diamonds. The locality of the specimen is shown in its name. Alaska Diamond Alencon Diamond Arkansas Diamond Baffa Diamond Bohemian Diamond Brazil or Brazilian Diamond Briancon Diamond Bristol Diamond Buxtom Diamond Cape May Diamond Cornish Diamond Dauphine Diamond False Diamond Fleurus Diamond Herkimer Diamond Horatio Diamond Hot Springs Diamond Irish Diamond Isle of Wight Diamond Lake George Diamond Marmoros Diamond Marmorosch Diamond Mora Diamond Occidental Diamond Paphos Diamond Pecos Diamond Pseudo-diamond Quebec Diamond Schaumberg Diamond Trenton Diamond Unripe Diamond Vallum Diamond Wicklow Diamond (c) "Pebble" or "Stone" indicative of the water-worn surface of crystal-clear quartz. Pebble. Brazilian Pebble. Bristol Stone. Coradgee Stone. Rain Stone—a double meaning of a water-worn pebble supposed to represent petrified rain-drops. Rhinestone. Show Stone. Vellum or Vallum Stone. (d) Other clear quartzes: Beryl—old name, applied particularly to engraved stones, only very rarely used with this meaning at the present time. Dragonite Water-worn quartz with brilliant luster, supposed to be Dragon's Eye petrified eyes of the mythological dragon. Jewel of Perfection Japanese term for rock crystal. Rock Quartz. White Sapphire. White Topaz. (2) Colored crystals, color usually uniform, but may be zoned or irregular in a single individual. (a) Violet, purple: Amethyst-typical name for this color. Occidental Amethyst-differentiates true amethyst (quartz) from other minerals of similar color. Oriental Amethyst is applied to exceptionally beautiful specimens of amethyst. Siberian Amethyst refers to a dark colored amethyst whose color by artificial light is fine red. Bishop's Stone. Lavendine. Soldier's Stone. (b) Blue, indigo: Azure Quartz. Sappharine. Sapphire usually applied to corundum gems, and when used in connection with quartz usually has that name added. Sapphire Quartz. Sapphirine. Siderite. Water Sapphire usually applied to cordierite gems, but also to quartz, rarely. (c) Yellow, golden: Citrine is the typical name for this color, and includes all quartz of yellow cast. Golden Quartz. Yellow Quartz. "Topaz"-much of the topaz of commerce is yellow quartz, or decolorized smoky quartz. Bohemian Topaz. Colorado Topaz. False Topaz. Golden Topaz. Indian Topaz. Maderia Topaz. Occidental Topaz. Saxon Topaz. Schnecken Topaz. (d) Smoky browns, smoky yellows: Smoky Quartz is typical of any smoke-like color. Cairngorm- -the Scotch name for particularly pellucid smoky quartzes, which is now applied to most which are suited for gems. Cairngorm Stone. Cairngorum alternate spellings adopted in different localities. Carngorn Scotch Pebble this term is also applied to small agates freed from the lavas, and worn by water to rough polish. Scotch Topaz. Smoke Stone. Smoky Topaz. (e) Color red: Arizona Ruby. Bohemian Ruby. Apricotine yellowish red. Hyacinth. Jacinto dark red. Mont Blanc Ruby. "Ruby" applied as is diamond to quartz of the color of true ruby, but always with a qualifying name to show origin. This use of ruby and diamond is quite distinct from that of topaz, which is adopted by jewellers [jewelers] as a name for yellow quartz. (f) Color black: Morion- -deep black, often almost opaque, but more usually will transmit light fairly well, and almost totally reflect angular light. (B) VARIETIES NAMED FROM PECULIARITIES OF CRYSTALLIZATION OR SHAPE. Most are of the rock-crystal variety, but the other types occur both colored and sagenitic varieties. (1) Parallel groupings and intergrowths of large individuals. Babel or Babbel Quartz- rock-crystal with flat pyramidal growths on the large pyramidal faces, the tiers of which have a fanciful resemblance to the tower of Babel. Cavernous Quartz with deep etched cavities parallel to the faces. Sceptre Quartz- -parallel grouping of small knob-shaped crystal atop a slender prism. (2) ?Fibrous groupings. Barrel Quartz- corrugated veinlets, whose sheaves of fitres are barrel-shaped. Cross-course Spar--radiated vein-quartz. Fibrous Quartz. Radiated Quartz. Drusy Quartz- small crystals in parallel growth, as crusts, or lining geodes, or in central part of veins. Globular Quartz porphyritic quartz phenocrysts in spherical outline, may be twins showing as spherical sectors or round individuals. Mineral Blossom drusy quartz. Potato Stone quartz geode. Twisted Quartz- simple quartz prism warped as through pressure and now made up of spirally arranged individuals. (C) VARIETIES NAMED FROM INCLUSIONS OF FOREIGN MINERALS. Sometimes in definite crystals, irregularly dispersed or arranged in adherence to crystallographic lines or planes; also inclusions of liquid or gas. (1) Crystalline inclusions. (a) Spangles: Aventurine is the common type name, and includes all spangled quartzes. Avanturine is an alternate spelling. Avanturine Quartz. Aventurine Quartz. Gold Quartz contains native gold in visible spangles. Gold Stone, yellow iron oxides, simulate gold. Hyacinth of Compostella, red hematite inclusions. Imperial Jade, green aventurine. Imperial Yu Stone, green actinolite (?) inclusions. Lizote, blue inclusions of silver ore. Rusty Quartz, discolored by iron oxides. Rubasse or Rubace-red hematite inclusions. This name is also applied to quartz stained red by artificial means. Sinople or Sinopal red hematite spangles. Sunstone, very rare variety with yellow spangles. (b) Needles: Sagenite is the type name, and rutile is the most common acicular mineral in sagenites. Byssolite, fine greenish actinolite or asbestus needles. Crispite. Cupid's Darts goethite inclusions. Fleches d' Amour—rutile needles. Hair Stone crowded full of a matted mass of acicular crystals. Hedgehog Stone radiated needles of geothite. Love Arrows rutile needles. Needle Stone. Onegite -goethite inclusions. Reticulated Quartz--rutile needles in rectangular patterns. Rutilated Quartz—rutile needles. Sagenitic Quartz. Thetis Hair Stone- -green acicular actinolite inclusions. Venus Hair Stone. (c) Fibres, usually parallel and yielding a cat's eye effect when cut across fibres; also sometimes showing asterism. Cat's eye is the type name. Asteria shows asterism. Asteriated Quartz. Cat's Quartz. "Crocidolite" applied to a replacement of the original crocidolite by quartz which retains enough of the silicate to color the replacement and often to give cat's eye effects. Crocidolite Quartz. Hawk Eye or Hawk's Eye, applied to crocidolite replacement. Hungarian Cat's Eye. Occidental Cat's Eye. Quartz Cat's Eye. Sapphire Quartz, blue because of crocidolite, often only faintly chatoyant, indicating an almost complete replacement of the fibrous crocidolite. Schiller Quartz. South African Cat's Eye crocidolite replacement. Starolite Star Quartz asteriated quartz. Star Stone Tiger's Eye, brownish to yellow crocidolite replacement, showing alteration previous to the introduction of silica. Wolf's Eye Stone. (d) Layers of clay or scaly mineral deposited on former crystal planes, which were covered by later deposits of the same orientation on the quartz crystal. Capped Quartz, in which the shells of quartz are separable. Cap Quartz. Ghost Quartz, in which the outline of the smaller crystal is visible. Phantom Quartz, in which chlorite grains show the smaller crystal. Skeletal Quartz, in which the smaller crystal is not of the same form as the outer one. (e) Densely distributed inclusions, usually this type is found in rocks of which silica is the major part, and the inclusions represent the residual of other minerals included in the original sediments. Ferruginous Quartz. Actinolitic Quartz. Arenaceous Quartz. Chloritic Quartz. Micaceous Ouartz. etc. (2) Liquid inclusions, usually of water, also carbon dioxide, or hydrocarbons, visible through the presence of a bubble of air or other gas which moves as the specimen is turned. Hydrolite. Water Stone. (3) Gaseous inclusions, often in films in cracks yielding an iridescent stone or more rarely in larger masses, showing when opened as pungent odors Cotterite has a metallic pearly luster and probably belongs here. Eldoradoite—an iridescent quartz. Iridescent Quartz. Iris—often natural, but may also be artificially produced. Chert Hornstone Sinter Siliceous Sinter Sil-sinter Quartz Sinter (4) Vein Quartz, usually of igneous origin. Bastard Quartz Bucks Quartz Buck Stone Dead Quartz Float Stone Mice-eaten Quartz. Spar Sucked Stone Sugar Spar Sugary Quartz IV. CRYPTOCRYSTALLINE VARIETIES OF SILICA Chalcedony is the type name, but this has been divided into several optically distinct types, as noted above. Usually very finely fibrous and sub-microscopic. Surface usually botryoidal, fracture hackly, luster waxy, translucent to opaque. (A) VARIETIES NAMED FROM COLOR. (1) Color uniform: Cacholong—whitish cloudy. Chalcedony is usually whitish, and is often used to refer to any uniformly colored specimen. Calcedony Chalcedon California Moonstone—white to gray. Moonstone usually applied to feldspar, also to white chalcedony. Mother Stone—whitish chalcedony. Occidental Chalcedony—somewhat opaque, whitish. Oriental Chalcedony very translucent white chalcedony. Rainbow Chalcedony—structurally in thin concentric layers, but of uniform color, may exhibit iridescence when cut across layers. White Agate—uniform white chalcedony. Mohava Moonstone—translucent lilac-hued chalcedony. Violite purple. Blue Chrysoprase—blue. Blue Moonstone blue. Keystoneite—blue. Sapphirine—blue chalcedony, note also that this is a silicate mineral, and is also applied to blue quartz. Zafirina—blue chalcedony. Chrysoprase—green translucent chalcedony. Jade—true jade is a silicate, but the term is often wrongly applied to green Cornelian Sardine Stone Sardine Sardius Sard—rich brown translucent chalcedony. Sardoine (2) Banded, color and structure, Agate is the type name, and refers to any banded chalcedony. (a) Straight bands: Onyx—is typical of straight bands one of whose colors is white. Carnelonyx—white and red bands. Carnelian Onyx—white with red bands. Chalcedony Onyx white and pale colored bands. Chalcedonyx—bands of gray and white. Nicolo-black or brown base, with bluish white top band. Onicolo Onychite Onyx Stone Oriental Onyx Oriental Sardonyx black base, white intermediate band and brown or red top layer. Sardagate—white and orange-red bands, may be semi-transparent. Sardian Onyx Sardian Stone Sardony Sard Onyx Sardonyx white and brown bands. Saturnine Onyx--with very dark lower band, giving the stone a dark appearance throughout. Amber Agate—yellowish, translucent. Amberine -yellowish green. Banded Agate. Blood Agate red to pink. Carnelian Agate with predominating bands of carnelian. Cer Agate—chrome-yellow. Occidental Agate. Oriental Agate finely marked and very translucent. Riband Agate—parallel bands. Ribbon Agate. Sardachate—with predominating bands of red carnelian. Semi-carnelian-yellow agate. Striped Agate wide parallel stripes. (b) Curving bands, often concentric, probably formed by successive layers deposited in spheroidal cavities, as in lavas. Eye Agate concentric rings, usually showing a dark center. Aleppo Stone Eye Stone Cyclops—a single large eye. Ring Agate concentric differently colored bands, often with pale chalce-donic center, or a druse. Rainbow Agate shows iridescence when cut across the concentric structure. (c) Broken bands, zigzag, or otherwise discontinuous. Brecciated Agate angular fragments of agate cemented by amethystine quartz. Fortification Agate -parallel zigzag lines, as though an agate broken and cemented by very narrow bands of chalcedonic silica. Ruin Agate—zigzag bands resembling ruins. (3) Colors mottled, perhaps due at times to inclusions but more often there is no disconuity of the silica, merely a changing of pigment. Catalinite green, red, and brown mottlings. Catalina Sardonyx. Cloudy (or Clouded) Agate. Cloudy (or Clouded) Chalcedony. Frost Stone gray ground, with scattered patches of white. Prismatic Moonstone cloudy chalcedony. Rice Stone a ground color spotted with white spots resembling rice grains. Sandy Sard—brown chalcedony spotted with darker browns. St. Stephen Stone with round blood-red spots. White Carnelian—cloudy white or very pale reddish. (A) VARIETIES DUE TO LUSTER. Wax Agate—yellow agate with pronounced waxy luster. (B) VARIETIES NAMED BECAUSE OF MECHANICAL INCLUSIONS. Some of the uniformly colored chalcedonies belong here because their color is due to some definite mineral, as the blues are often due to chrysocolla, but their name is applied to the color and not the impurity. Many impurities are dendritic. (1) Dendritic inclusions: Moss Agate is the type name for dendritic chalcedony. Dendritic Agate. Fancy Agate—with particularly delicate markings. Flower Stone when the dendrites are flower-like. Indian Agate Mocha Pebble Mocha Agate Mocha Stone Montana Agate River Agate Scenic Agate—when the dendrites suggest landscapes. Tree Agate dendrites resemble trees. Tree Stone. (2) Other solid inclusions: Myrickite—bright red cinnabar inclusions. Opal Agate alternating layers of opal and chalcedony. (3) Other inclusions of liquid or gas. Perhaps the iridescence of Rainbow Chalcedony and Agate are due to thin air films between the concentric layers. Enhydros—follow nodules of chalcedony partly filled with water. Water Agate shell of chalcedony containing a bubble of water. (D) ARTIFICALLY [ARTIFICIALLY] ALTERED CHALCEDONY AND AGATE. This mineral is porous enough to absorb dyes, and agate is often differentially porous so that different layers will absorb different dyes, yielding a varicolored product. Colors are, like quartz, altered by heat. Burnt Carnelian color made red by heating. Burnt Stone Emeraldine—stained green. False Lapis stained blue. Swiss Lapis V. MIXTURES AND INTERGROWTHS OF QUARTZ, JASPER AND CHALCEDONY Some of these close associations of the varieties of silica suggest that quartz is an ultimate product of recrystallization which may take place after very long periods of time. Agate Jasper intermediate between jasper and chalcedony, a close mixture, often banded or veined. Hemachate-light colored chalcedony spotted with red jasper. Hyaline Quartz—quartz with bluish opalescent cast due to the presence of chalcedony. Jaspagate—opaque jasper with chalcedonic inclusions. Jasponyx—onyx, part of whose layers are jasper and part chalcedony. Kinradite—jasper with spherulites of quartz. Texas Agate—agate jasper. VI. PSEUDOMORPHOUS SILICA (A) ORGANIC PSEUDOMORPHS. Many fossils are preserved by silicification of their softs parts, or of their calcareous shells and bones. Particular names are given to: Fossil Coral Beckite Coral Agate Petoskey Agate Beekite Orbicular Silica Petrified Honeycomb Silicified Wood Agatized Wood Jasperized Wood Shinarump Chinarump Petrified Wood Wood Agate Wood Stone (B) SILICA REPLACING OTHER MINERALS, as fluorite, barite, etc., but definite names for such replacements are limited to Haytorite chalcedonic replacement of datolite. VII. ROCKS, AND OTHER MIXTURES PREDOMINATELY SILICEOUS The rocks listed in III-(C) often contain appreciable impurities and also may consist wholly of silica. Many other rocks contain large proportions of silica, particularly the acid igneous rocks, of which possibly vein quartz is an extreme. Most sedimentary rocks, except limestones and coal, contain large amounts of detrital quartz. Most metamorphics also carry large percentages of free silica, both as recrystallized material from the sediments, and as material added by the metamorphic agencies. Furthermore, quartz is an important part of many weathering products, allu viums, gossans, etc. BARYTOCELESTITE FROM THE KINGDEN LEAD MINES, GALETTA, ONTARIO Galena and sphalerite occur in many places in eastern Ontario. A common type of occurrence is in well defined veins which cut vertically through beds as late as Ordovican. The veins show a decided banding with many vuggy openings along the central part. The greater part of the vein-filling is calcite in which the galena commonly occurs in crystals arranged more or less continuously along certain planes, but the planes are not themselves continuous. Sphalerite is intergrown with galena in varying pro-portions. The vuggy openings in the central part of some of the veins show a variety of minerals of the later vein stages. At the old Frontenac lead mine at Perth Road, Frontenac County, the openings in the vein contain well formed crystals of sky-blue celestite up to two inches in length. Marcasite is one of the late minerals to crystallize. At Galetta, west of the City of Ottawa, a vein of this type has been worked for some years for its lead content. At places the well banded calcite vein is open along the medial line. At other places the central part is filled with very transparent selenite which forms crystals as much as a foot in length. The galena is well crystallized. It carries some brown sphalerite distributed as fine grains through the galena crystals. In the open spaces barite of a light brownish color covers the surface of the calcite. Later than the barite and distributed as rosettes on its surface is marcasite and later again are small nests or tufts of needle shaped crystals of a sulphate that contains both barium and strontium. The relation of the water, and a later period of clear selenite, that in places occupies the central part of the vein, to the barytocelestite is not definitely known as the two have not vet been seen together. The deposition of the vein minerals, therefore, took place in an early ore stage in which calcite and galena were deposited in alternating zones deposition of sulphates and marcasite in the vein cavities. The order of crystallization in this last stage was barite, marcasite, barytocelestite, and selenite with the period of the last two not definitely known. The barytocelestite is in needle-like crystals with the shorter measurements from 0.08 mm. to 0.1 mm. The length is approximately ten times as great. A chemical analysis of as pure material as could be obtained gave the following result. Ba SO4, 81.5 per cent Sr SO4 18.5 100.00 Qualitative tests for calcium gave negative results and in the above analysis only barium was determined and the strontium sulphate was assumed to make up the remainder. From this the formula appears to be approximately 5BaSO4 • SrSO4. Optical examination shows that the value of the index of refraction for vibrations parallel to the longer direction of the crystal is 1.63 and that this is greater than the index for the shorter direction. The interference color is ordinarily slate gray and assuming a thickness of 0.1 mm. the birefringence is 0.001 and the value for the index of refraction in the shorter direction is 1.629. It is likely that in the refractive index liquids the crystals are lying on the base and hence these two values are the least and mean indices with the mean index that for the direction parallel to the elongation of the crystal. By analogy with barite and celestite this would be the b crystallographic axis. Walker1 has described a stalactitic barite from Madoc which carries 13.95 per cent SrO. This mineral he states is later than the flurite and incrusts it. The succession of minerals at Galetta shows an interesting variation in the vein forming solutions. During the main ore stage the solutions deposited sulphides and carbonates. Then came the sulphates with barium sulphate as the first to form followed by either the strontium or the calcium sulphates. Celestite occurs in nodules in the Palaeozoic limestones in the vicinity of Kingston. These are neither in nor near veins but apparently formed by segregation of the celestite during the formation of the limestone. If the celestite nodules are contemporaneous with the limestone it seems possible that the presence of strontium in the vein forming solutions during the later stages of formation of the Galetta and Perth Road lead veins may be due to admixture of the original 1 Am. Mineral., Volume 4, page 79 (1919). galena-bearing solutions, possibly from deep seated sources, with shallow water solutions which had dissolved from the limestones some of their strontium content. This is in agreement with the hypothesis suggested by Uglow for the calcite-barite-fluorite-galena veins of this district. He? assigns these deposites to solutions in part of meteoric, in part of magmatic origin. THE FLORENCE METEORITE OF WILLIAMSON COUNTY, TEXAS JOHN T. LONSDALE, University of Texas. The Florence Meteorite, the history of which is given below,' is of interest because of its excellent state of preservation and petrographic characters. The stone was a small one, measuring 11.5X14X11 cm. and weighed 3640 grams before cutting. The shape was roughly rectangular with four faces approximately plane the other two being rounded. All faces except the rounded ones show the characteristic pitted surfaces, the largest pits being 2 cm. in greatest dimensions. The unbroken surface of the stone is black while the interior is light gray. The black surface material is present as an exceedingly thin skin of oxidation. Plate I, figure 2 shows the external features of the meteorite. 2 Ontario Bureau of Mines, Volume XXV, Part No. 2, page 40. 1 The meteorite fell on the night of January 21, 1922 on the farm of T. H. Lindsey, five miles northeast of Florence, Williamson County, Texas. The stone subsequently came into the possession of Dr. F. W. Simonds of the University of Texas to whom the writer is indebted for details concerning the history of the fall and for the opportunity of studying the specimen. Through the kindly offices of Dr. G. P. Merrill of the U. S. National Museum the stone was cut, sectioned, and analyzed. One half of the meteorite and a cast are deposited in the U. S. National Museum while the other half and a second cast remain in the collections of the University of Texas. Details concerning the fall of the stone show that it fell at about 8 p. M. after darkness had come on. The direction was from the southwest and the fall was accompanied by a noise "almost like thunder and a great light streak toward the west." The stone fell on the edge of a dry water-course covered with cobbles and "did not knock much of a hole in the ground." The stone was found the next morning ten or twelve hours after the fall. The latitude and longitude of the locality as nearly as can be stated are 30° 52' north and 97° 43' west. Thin sections show the stone to be a chondrite with several kinds of chondru | |
