DOCSLIB.ORG

9/16 Weathering Notes

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
9/16 Weathering Notes EAS 3030 9/16/08 LAD Weathering reactions We can consider many weathering reactions as acid-base reactions. Acidity in soils can be generated from several sources. The main ones are: • Hydration of CO2 (yields carbonic acid): CO2 + H2O H2CO3 • Organic decomposition to yield organic acids (R-COOH R-COO- + H+) • Sulfide oxidation to yield sulfuric acid (2FeS2+4H2O+7.5O2 4H2SO4+Fe2O3) • Atmospheric deposition of mineral acids such as H2SO4 and HNO3. The hydrogen ion released by these acids can react with carbonate minerals (e.g. CaCO3) or alumino-silicate minerals (feldspars, micas, clays ….). Carbonate and silicate weathering reactions can be considered separately: For carbonates, we can write: ++ - 1) CaCO3 + H2 CO3 Ca + 2HCO3 In this reaction carbonic acid (from CO2 and water) and calcium carbonate react to form bicarbonate ion and calcium ion. The net reaction yields no H+, so the carbonic acid has been neutralized by reaction with carbonate. It also yields no solid phases – the carbonate mineral undergoes complete dissolution. This sort of reaction is know as “congruent” dissolution. An example silicate reaction would be the reaction of potassium feldspar (a primary mineral) to form kaolinite, a secondary mineral . The reaction of a primary mineral to form a secondary mineral plus solutes is called “incongruent” dissolution. + + 2) 2KAlSi3O8(Kspar) + 2H + 9H2O Al2Si2O5(OH)4(kaol) + 4H4SiO4(aq) +2K If the source of acidity is CO2, we can write equivalently: + - 3) 2KAlSi3O8(Kspar) + 2CO2 + 11H2O Al2Si2O5(OH)4(kaol) + 4H4SiO4(aq) +2K + 2HCO3 In the breakdown of K-feldspar, acidity is consumed. We can see that H+ is used up and K+ is released to solution, a kind of “ion exchange” reaction. Also released to solution is dissolved silica or silicic acid, written H4SiO4. As a general observation, we can say that acids are neutralized (H+ consumed) by weathering minerals. The reaction products are “base cations” (Na+, K+, Ca++, Mg++), and - if CO2 is the acid another product will be bicarbonate ion (HCO3 ). In the case of alumino-silicate weathering, silicic acid (a.k.a. “dissolved silica”) is released as well. Secondary alumino-silicate minerals are typically clays, and have increased hydroxyl and/or water content, relative to their primary precursors. 1 EAS 3030 9/16/08 LAD Because of its low solubility in typical environments, aluminum is often largely retained in the secondary mineral. It is sometimes a useful approximation to treat Al as a “conservative” element, i.e. one that does not enter or leave the system of interest. We can then normalize the other elements in a mineral to the Al content to examine net mass transfer. For example, in reaction 2, we can write: Table 1 Si/Al K/Al H/Al K-feldspar 3 1 0 kaolinite 1 0 2 Since Al is neither gained nor lost in this reaction, it serves as an index element for the others. The secondary kaolinite is depleted in Si and K relative to the primary mineral, but enriched in H (as hydroxyl). Typically secondary clay minerals have increased molar volumes (lower densities) than primary alumino-silicates. An equilibrium constant for reaction #2 can be written 4): 2 + 4 [K ] [H4 SiO4 ] K'= 2 [H + ] by taking the square root of both sides we can reduce it to 5) ! + [K ] 2 K = [H4 SiO4 ] [H + ] Taking logarithms, we can write ! " [K + ]% 6) logK = log$ ' + 2log[H4 SiO4 ] # [H + ]& + + We can make a plot with log[H4SiO4] for the “x” axis and log([K ]/[H ]) for the “y” axis. Then equation 6 has the form of a straight line y = mx + b with a slope m of -2 and a “y” int!e rcept of logK: " [K + ]% 7) log$ ' = (2log[H4 SiO4 ]+ logK # [H + ]& The value of logK can be found in some tables of geochemical data, or calculated from thermodynamic data for the Gibbs free energy of formation (∆G˚f) of the reactants and pr!oduc ts: 2 EAS 3030 9/16/08 LAD 8) ∆G˚reaction = ∑∆G˚f(products) - ∑∆G˚f(reactants) !"G 0 9) log K = r 2.303RT -1 -1 -1 The value of R = 8.3143 J mol K , so if the ∆G˚f data are given in kilojoules per mole (kJ/mole) and the temperature is 25˚C (298.15 K), equation 9 can be simplified to: -1 10) logK = - ∆G˚reaction/5.708 kJ mol . Gibbs free energy of formation data for some of the phases we will work with are in the table below: Table 2 0 phase formula ∆Gf , kJ/mole gibbsite Al(OH)3 -1151 kaolinite Al2Si2O5(OH)4 -3800 pyrophyllite Al2Si4O10(OH)2 -5275 muscovite KAl3Si3O10(OH)2 5606 K-feldspar KAlSi3O8 -3767 albite NaAlSi3O8 -3715 analcite NaAlSi2O6•H2O -3090 Na-beidellite Na0.33Al2.33Si3.67O10(OH)2 -5382 K+ -283.27 Na+ -261.91 H4SiO4 -1316.6 H2O -237.13 Ca2+ -553.58 H+ 0 Data from J. I. Drever, 1997, The Geochemistry of Natural Waters, Prentice Hall For reaction 2 (Kspar -> kaolinite) the ∆G˚reaction is given by the “products minus reactants” (with proper stoichiometric weighting), and will be: 11) ∆G˚reaction = [-3800 + 2(-283.27) + 4(-1316.6)] - [2(-3767) + 2(0) + 9(237.13)] = 35.23 kJ mol-1. Using equation 9: -1 -1 -1 12) log K’Kspar-kaol = -35.23 kJ mol /(2.303 × 8.3143 kJ mol K × 298.15 K) = -6.17 3 EAS 3030 9/16/08 LAD Since K = √K’, from the properties of logarithms we have that 13) log K = log K’/2 i.e. log K = -6.17/2 = -3.09 Note that, although we found it convenient to reduce the order of the equation 4 to equation 5, we must still calculate ∆G˚reaction according to the stoichiometry we have written for equation 2. But, note also we could have equally well written equation 2 in an alternative but still balanced fashion: + + 14) KAlSi3O8 + H + 4.5H2O 0.5Al2Si2O5(OH)4 + K + 2 H4SiO4 which would lead directly to the definition of K in equation 5. The two approaches are equivalent and thermodynamically consistent. Now we have numerical values for both the slope of this reaction line (-2) and it’s + + y-intercept (-3.09) on a plot of log([K ]/[H ]) vs. log([H4SiO4]). What does this look like? See Figure 1. Follow the accompanying Powerpoint graphics with the equations below as we build the stability relations for the system K-Al-Si-H2O. In order to complete the system, we will consider the following phases and the reactions between them: K-feldspar, kaolinite, muscovite and gibbsite. We will also include opal (amorphous silica). The next reaction we write is kaolinite to gibbsite: 15) Al2Si2O5(OH)4 (kaol) + 5H2O 2Al(OH)3 (gibb) + 2 H4SiO4 Unlike the K-spar reaction, this is not an acid-base reaction. Gibbsite is an “end-product” of weathering, completely stripped of base cations, and silica, leaving only the highly insoluble aluminum hydroxide. It is typically found in highly weathered tropical soils. The equilibrium constant for this reaction is simply; 2 16) K’(kaol-gibb) = [H4SiO4] From the data in Table 2, we can write -1 17) ∆G˚reaction = [-3800 + 5(-237.13)] - [2(-1151) + 2(-1316.6)] = 50.45 kJ mol . From equation 10 we obtain -1 -1 18) log K’(kaol-gibb) = -50.45 kJ mol /(5.708 kJ mol ) = -8.8 19) K = √K’= [H4SiO4] 4 EAS 3030 9/16/08 LAD 20) log K = logK’/2 = -4.4 (i.e has a numerical value of 10-4.4). + + On the plot of log([K ]/[H ]) vs. log[H4SiO4], the equilibrium boundary appears as a straight vertical line (i.e. undefined slope) with an “x-intercept” of –4.4 (Figure 2). The next reaction we add is between muscovite and K-feldspar. Muscovite is a mica, and can be a primary mineral. The mineral illite, a fine-grained clay is chemically and structurally very similar to muscovite, and is commonly a secondary mineral. Here we use the thermodynamic data for muscovite. + + 21) 3KAlSi3O8(Kspar) + 2H + 12H2O Kal3Si3O10(OH)2 (muscl) + 4H4SiO4(aq) +2K The equilibrium constant is [K + ]2 22) K'= [H SiO ]6 [H + ]2 4 4 + [K ] 3 23) KKspar"musc = + [H4 SiO4 ] ! [H ] Using data from Table 2 we find that ∆Grxn = 74.42 kJ mol-1, logK’ = -13.0, and logKkspar-musc = -6.5. As for equation 7, we can write: ! + + 24) log([K ]/[H ]) = -3log[H4SiO4] + logKkspar-musc Thus, on our chosen axes, the reaction boundary between K-spar and muscovite will have a slope of –3 and a y-intercept of –6.5 (Figure 3). Because they have different slopes, the K-spar - muscovite reaction boundary intercepts the K-spar - kaolinite line. Thus, depending on both initial conditions and the reaction path, K-spar could react to form either muscovite or kaolinite. As we complete the diagram we will be better able to see which reaction is relevant for a given set of conditions. Muscovite may also react to form gibbsite: + + 25) KAl3Si3O10(OH)2 (muscl) + H + 9H2O 3Al(OH)3 (gibb) + K + 3H4SiO4 The equilibrium constant is [K + ] 26) K = [H SiO ]3 musc"gibb [H + ] 4 4 and we obtain directly ! + + 27) log([K ]/[H ]) = -3log[H4SiO4] + logKmusc-gibb 5 EAS 3030 9/16/08 LAD From table 2, the value of ∆Grxn = 74.42 kJ mol-1, and logKmusc-gibb = -9.5. The muscovite-gibbsite reaction boundary will plot as a line with a slope of –3 and an intercept of –9.5, and is parallel to the K-spar-muscovite line (figure 4). Muscovite may also react to form kaolinite: + + 28) 2KAl3Si3O10(OH)2 (muscl) + 2H + 3H2O 3Al2Si2O5(OH)3 (gibb) + 2K The equilibrium constant is: [K + ]2 29) K'= [H + ]2 [K + ] 30) Kmusc"kaol = + ! [H ] Following the usual procedure with data from Table 2, we obtain logKmusc-kaol = 3.8.
Load more

Recommended publications
  • Clay Minerals Soils to Engineering Technology to Cat Litter
    Clay Minerals Soils to Engineering Technology to Cat Litter USC Mineralogy Geol 215a (Anderson) Clay Minerals Clay minerals likely are the most utilized minerals … not just as the soils that grow plants for foods and garment, but a great range of applications, including oil absorbants, iron casting, animal feeds, pottery, china, pharmaceuticals, drilling fluids, waste water treatment, food preparation, paint, and … yes, cat litter! Bentonite workings, WY Clay Minerals There are three main groups of clay minerals: Kaolinite - also includes dickite and nacrite; formed by the decomposition of orthoclase feldspar (e.g. in granite); kaolin is the principal constituent in china clay. Illite - also includes glauconite (a green clay sand) and are the commonest clay minerals; formed by the decomposition of some micas and feldspars; predominant in marine clays and shales. Smectites or montmorillonites - also includes bentonite and vermiculite; formed by the alteration of mafic igneous rocks rich in Ca and Mg; weak linkage by cations (e.g. Na+, Ca++) results in high swelling/shrinking potential Clay Minerals are Phyllosilicates All have layers of Si tetrahedra SEM view of clay and layers of Al, Fe, Mg octahedra, similar to gibbsite or brucite Clay Minerals The kaolinite clays are 1:1 phyllosilicates The montmorillonite and illite clays are 2:1 phyllosilicates 1:1 and 2:1 Clay Minerals Marine Clays Clays mostly form on land but are often transported to the oceans, covering vast regions. Kaolinite Al2Si2O5(OH)2 Kaolinite clays have long been used in the ceramic industry, especially in fine porcelains, because they can be easily molded, have a fine texture, and are white when fired.
    [Show full text]
  • Removal of Iron-Bearing Minerals from Gibbsitic Bauxite by Direct Froth Flotation
    a Original Article http://dx.doi.org/10.4322/2176-1523.0924 REMOVAL OF IRON-BEARING MINERALS FROM GIBBSITIC BAUXITE BY DIRECT FROTH FLOTATION Felipe de Melo Barbosa 1 Maurício Guimarães Bergerman 2 Daniela Gomes Horta 3 Abstract The refractory bauxite needs to present less than 2.5% of Fe2O3 to be applied in the ceramics industry. The depletion of high Al2O3 grade deposits has stimulated the improvement of bauxite concentration methods in order to remove iron-bearing minerals. The objective of this study was to evaluate the influence of collector dosage, pH and milling time on the gibbsite flotation performance. Firstly, the sample mineralogical composition was determined by means of X-ray diffraction (XRD) and binocular loupe analysis. X-ray fluorescence (XRF) analysis was used to determine the sample chemical composition. Flotation was then accomplished by using hydroxamate as gibbsite collector, sodium silicate as silicate depressant and starch as iron-bearing minerals depressant. The bauxite Fe2O3 content was reduced from 7.66% to 4.81-5.03%. In addition, the flotation performance decreased by diminishing the pH from 9.5 to 8.5 or increasing the pH to 10.5. The milling time influence on the flotation indicates that the presence of slime can significantly affect the gibbsite concentration. Keywords: Bauxite; Gibbsite; Direct flotation; Hydroxamate. REMOÇÃO DE MINERAIS PORTADORES DE FERRO DE BAUXITA GIBSÍTICA POR FLOTAÇÃO DIRETA Resumo As bauxitas refratárias precisam apresentar teores de ferro menores que 2,5% para serem utilizadas na indústria de cerâmica. A exaustão dos depósitos com altos teores de Al2O3 tem estimulado a pesquisa por métodos de concentração de bauxita de forma a remover os minerais portadores de ferro.
    [Show full text]
  • Part 629 – Glossary of Landform and Geologic Terms
    Title 430 – National Soil Survey Handbook Part 629 – Glossary of Landform and Geologic Terms Subpart A – General Information 629.0 Definition and Purpose This glossary provides the NCSS soil survey program, soil scientists, and natural resource specialists with landform, geologic, and related terms and their definitions to— (1) Improve soil landscape description with a standard, single source landform and geologic glossary. (2) Enhance geomorphic content and clarity of soil map unit descriptions by use of accurate, defined terms. (3) Establish consistent geomorphic term usage in soil science and the National Cooperative Soil Survey (NCSS). (4) Provide standard geomorphic definitions for databases and soil survey technical publications. (5) Train soil scientists and related professionals in soils as landscape and geomorphic entities. 629.1 Responsibilities This glossary serves as the official NCSS reference for landform, geologic, and related terms. The staff of the National Soil Survey Center, located in Lincoln, NE, is responsible for maintaining and updating this glossary. Soil Science Division staff and NCSS participants are encouraged to propose additions and changes to the glossary for use in pedon descriptions, soil map unit descriptions, and soil survey publications. The Glossary of Geology (GG, 2005) serves as a major source for many glossary terms. The American Geologic Institute (AGI) granted the USDA Natural Resources Conservation Service (formerly the Soil Conservation Service) permission (in letters dated September 11, 1985, and September 22, 1993) to use existing definitions. Sources of, and modifications to, original definitions are explained immediately below. 629.2 Definitions A. Reference Codes Sources from which definitions were taken, whole or in part, are identified by a code (e.g., GG) following each definition.
    [Show full text]
  • Boehmite and Gibbsite Nanoplates for the Synthesis of Advanced Alumina Products † ‡ † † § Xin Zhang,*, Patricia L
    Article Cite This: ACS Appl. Nano Mater. 2018, 1, 7115−7128 www.acsanm.org Boehmite and Gibbsite Nanoplates for the Synthesis of Advanced Alumina Products † ‡ † † § Xin Zhang,*, Patricia L. Huestis, Carolyn I. Pearce, Jian Zhi Hu, Katharine Page, § ∥ † † Lawrence M. Anovitz, Alexandr B. Aleksandrov, Micah P. Prange, Sebastien Kerisit, † † † † ⊥ Mark E. Bowden, Wenwen Cui, Zheming Wang, Nicholas R. Jaegers, Trent R. Graham, † § § Mateusz Dembowski, Hsiu-Wen Wang, Jue Liu, Alpha T. N’Diaye,% Markus Bleuel,& ∥ † ‡ † # David F. R. Mildner,& Thomas M. Orlando, Greg A. Kimmel, Jay A. La Verne, Sue B. Clark, , † and Kevin M. Rosso*, † Pacific Northwest National Laboratory, Richland, Washington 99354, United States ‡ Radiation Laboratory and Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States § Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States ∥ School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States ⊥ # The Voiland School of Chemical and Biological Engineering and Department of Chemistry, Washington State University, Pullman, Washington 45177, United States %Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States &National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States *S Supporting Information ABSTRACT: Boehmite (γ-AlOOH) and gibbsite (α-Al- (OH)3) are important archetype (oxy)hydroxides of alumi- num in nature that also play diverse roles across
    [Show full text]
  • Compression Studies of Gibbsite and Its High-Pressure Polymorph
    Phys Chem Minerals (1999) 26: 576±583 Ó Springer-Verlag 1999 ORIGINAL PAPER E. Huang á J.-F. Lin á J. Xu á T. Huang Y.-C. Jean á H.-S. Sheu Compression studies of gibbsite and its high-pressure polymorph Received: 28 September 1998 / Revised, accepted: 22 December 1998 Abstract Various X-ray diraction methods have been Introduction applied to study the compression behavior of gibbsite, Al(OH) , in diamond cells at room temperature. A phase 3 The water reservoir in the Earth's mantle may be do- transformation was found to take place above 3 GPa minately hosted in the hydrous minerals (e.g., Akimoto where gibbsite started to convert to its high-pressure and Akaogi 1984). Therefore, the study of hydrous polymorph. The high-pressure (HP) phase is quenchable minerals at high-pressure and temperature is crucial for and coexists with gibbsite at the ambient conditions after understanding the dynamic processes of water circula- being unloaded. This HP phase was identi®ed as nor- tion in the mantle. Examples such as triggering deep dstrandite based on the diraction patterns obtained at focus earthquakes (Kirby 1987; Meade and Jeanloz room pressure by angle dispersive and energy dispersive 1991) and regulating the water budget have been docu- methods. On the basis of this structural interpretation, mented in hydrous minerals under mantle environments. the bulk modulus of the two polymorphs, i.e., gibbsite In the past few years, some hydrous minerals with and nordstrandite, could be determined as 85 5 and trioctahedral layer structure such as brucite (Mg(OH) ) 70 5 GPa, respectively, by ®tting a Birch-Murnaghan 2 (e.g., Duy et al.
    [Show full text]
  • Reaction of Aluminum with Water to Produce Hydrogen
    Reaction of Aluminum with Water to Produce Hydrogen A Study of Issues Related to the Use of Aluminum for On-Board Vehicular Hydrogen Storage U.S. Department of Energy Version 2 - 2010 1 CONTENTS EXECUTIVE SUMMARY ……………………………………………………………….. 3 INTRODUCTION ………………………………………………………………………… 5 BACKGROUND ………………………………………………………………………….. 5 REACTION-PROMOTING APPROACHES ………………………………………….. 6 Hydroxide Promoters Oxide Promoters Salt Promoters Combined Oxide and Salt Promoters Aluminum Pretreatment Molten Aluminum Alloys PROPERTIES OF THE ALUMINUM-WATER REACTIONS RELATIVE ……….. 14 TO ON-BOARD SYSTEM PROPERTIES Hydrogen Capacities Kinetic Properties System Considerations REGENERATION OF ALUMINUM-WATER REACTION PRODUCTS …………. 17 SUMMARY ………………………………………………………………………………. 19 REFERENCES …………………………………………………………………………… 20 APPENDIX I – THERMODYNAMICS OF ALUMINUM-WATER REACTIONS … 23 APPENDIX II – ORGANIZATIONS PRESENTLY INVOLVED WITH ………….. 26 HYDROGEN GENERATION FROM ALUMINUM-WATER REACTIONS 2 Reaction of Aluminum with Water to Produce Hydrogen 1 2 John Petrovic and George Thomas Consultants to the DOE Hydrogen Program 1 Los Alamos National Laboratory (retired) 2 Sandia National Laboratories (retired) Executive Summary: The purpose of this White Paper is to describe and evaluate the potential of aluminum-water reactions for the production of hydrogen for on-board hydrogen-powered vehicle applications. Although the concept of reacting aluminum metal with water to produce hydrogen is not new, there have been a number of recent claims that such aluminum-water reactions might be employed to power fuel cell devices for portable applications such as emergency generators and laptop computers, and might even be considered for possible use as the hydrogen source for fuel cell-powered vehicles. In the vicinity of room temperature, the reaction between aluminum metal and water to form aluminum hydroxide and hydrogen is the following: 2Al + 6H2O = 2Al(OH)3 + 3H2.
    [Show full text]
  • Minerals Found in Michigan Listed by County
    Michigan Minerals Listed by Mineral Name Based on MI DEQ GSD Bulletin 6 “Mineralogy of Michigan” Actinolite, Dickinson, Gogebic, Gratiot, and Anthonyite, Houghton County Marquette counties Anthophyllite, Dickinson, and Marquette counties Aegirinaugite, Marquette County Antigorite, Dickinson, and Marquette counties Aegirine, Marquette County Apatite, Baraga, Dickinson, Houghton, Iron, Albite, Dickinson, Gratiot, Houghton, Keweenaw, Kalkaska, Keweenaw, Marquette, and Monroe and Marquette counties counties Algodonite, Baraga, Houghton, Keweenaw, and Aphrosiderite, Gogebic, Iron, and Marquette Ontonagon counties counties Allanite, Gogebic, Iron, and Marquette counties Apophyllite, Houghton, and Keweenaw counties Almandite, Dickinson, Keweenaw, and Marquette Aragonite, Gogebic, Iron, Jackson, Marquette, and counties Monroe counties Alunite, Iron County Arsenopyrite, Marquette, and Menominee counties Analcite, Houghton, Keweenaw, and Ontonagon counties Atacamite, Houghton, Keweenaw, and Ontonagon counties Anatase, Gratiot, Houghton, Keweenaw, Marquette, and Ontonagon counties Augite, Dickinson, Genesee, Gratiot, Houghton, Iron, Keweenaw, Marquette, and Ontonagon counties Andalusite, Iron, and Marquette counties Awarurite, Marquette County Andesine, Keweenaw County Axinite, Gogebic, and Marquette counties Andradite, Dickinson County Azurite, Dickinson, Keweenaw, Marquette, and Anglesite, Marquette County Ontonagon counties Anhydrite, Bay, Berrien, Gratiot, Houghton, Babingtonite, Keweenaw County Isabella, Kalamazoo, Kent, Keweenaw, Macomb, Manistee,
    [Show full text]
  • Appendix I Glossary of Mining and Related Terms Relevant to Mine Water
    APPENDIX I GLOSSARY OF MINING AND RELATED TERMS RELEVANT TO MINE WATER SCIENCE AND ENGINEERING The glossary which follows is drawn from the experience of the authors, and represents terminology which was current in the English-speaking mining world at the start of the 21st Century. The glossary is restricted to mining and geological terms likely to be heard in the context of mine water management. We do not provide a general geochemical or hydrological glossary. Neither is this a thoroughly exhaustive glossary of mining engi- neering. The reader seeking a general mining glossary is referred to works such as Greenwell (1888), Orchard (1991) or Rieuwerts (1998). The glossary is not intended to cover geological and chemical terminology, with the exception of a few terms restricted largely to mining applications of these sciences. In the definitions which follow, words are underlined where they are themselves defined elsewhere in this glossary. Acid mine drainage Water which became acidic during its passage through pyrite- bearing mined strata. Synonym: “acid rock drainage”. Acid rock drainage See “acid mine drainage”. The term “acid rock drainage” is used predominantly in Canada, with the implication that the acidity problem is due to the rocks rather than the process of mining. There are at least two reasons why this usage is objectionable: (i) “Acid rocks” sensu stricto are a group of igneous rocks which are not noted for giving rise to problematic drainage. (ii) It is somewhat disingenuous to attempt to exonerate mining in this manner, as acidic drainage is relatively rare in unmined sulphidic strata, but is common where mining has increased the rock mass permeability and allowed oxygen to access previously reduced strata.
    [Show full text]
  • Minerals of Rockbridge County, Virginia
    VOL. 40 FEBRUARYJMAY 1994 NO. 1 &2 MINERALS OF ROCKBRIDGE COUNTY, VIRGINIA D. Allen Penick, Jr. INTRODUCTION RockbridgeCountyhas agreatdiversityofrocksandminerals.Rocks withinthecountyrangeingeologic agehmPmxnbrianthroughDevonian (01desttoyoungest)covexingatimespanofatleast 1OOOmilIion years. The county liesmostlywithintheVdeyandRiagePhysi~hich~~ 1). Thisprovinceis underlainbysedimentaryrochcomposedof dolostone, limestone, sandstone, andshale. TheexlMlceastempartofRockbridge County is withintheBlueRidge PhysiowhicPro. This areaisrepre sentedbyallthreemajorrocktypes: sedirnentary,igneous, andmetarnorphic. Theseinclu&Qlostone,qdta,inta~s~neandshale,granite, pmdiorite, andunakite. Ingeneral, theol&strocksarefoundin theeastem portion with youngerrocks outcropping in the westernpart of thecounty o%w2). Mininghasplaydan~tpaainthehistoryofRockbridgeCounty. Indians probably were thefirstco1lectorsof localqu~andquartzitefrom which they shapedprojectilepoints. Important deposits of ironore were mined in the 1800s near the towns of Buena Vista, Goshen, Vesuvius, and in Amoldvalley. Other early minesin thecounty -&manganese, waver- tine-marl, tin, niter (saltpeter), lithographiclimestone, silicasand, andcave orryx Thecounty has been prospected for barite, gibbsite (alumina), gold, silver, limonik(ocher),beryl, Ghalerite (zinc), andilmeniteandmtile(tita- nium), but no production has beenreported for t.Quarriesare still producing dolostone.lirnestone, andquartzitefor constructionaggregate andshale forbrickmanufacture. This report describes 102mineralsandnativeelements
    [Show full text]
  • Relative Stabilities of Soil Minerals
    552.12:553.08:631.416.4/. MEDEDELINGEN LANDBOUWHOGESCHOOL WAGENINGEN • NEDERLAND • 80-16(1980) RELATIVE STABILITIES OF SOIL MINERALS (with a summary in English) E. L. MEIJER and L. VAN DER PLAS Department of Soil Science and Geology, Agricultural University, Wageningen, The Netherlands (Received 5-IX-1980) H. VEENMAN & ZONEN B.V. - WAGENINGEN - 1980 RELATIVE STABILITIES OF SOIL MINERALS INTRODUCTION The stability of soil minerals is frequently considered in the geochemical literature (WILDMAN et al., 1971; KITTRICK, 1971a, 1971b; RAIan d LINDSAY, 1975; CURTIS, 1976; WEAVER et al., 1976; REESMAN, 1978). In most cases the possible composition of the aqueous solution coexisting with acertai n mineral is discussed in detail, thecompositio n being given in terms of activities ofth e relevant species in solution. The Gibbs free-energy change ofsuc h a reversible dissolution equilibrium is zero ifa n infinitely small amount ofth e mineral dissolves ((AG)R = 0). There­ fore, the mineral isonl y stable if for any other possible mineral made of com­ ponents present inth e system (AG)R ^ 0. It is quite understandable that the second part of this statement is rather difficult to investigate. The present paper will consider the importance ofthi s aspect. The Gibbs free-energy of formation of a mineral from itscomponent s ina well - defined system, e.g.,a n actual aqueous solution at 25° Can d 1bar , isindicate d by AG°el inthi s text. AG°el canb euse d to quantitatively describe the relative stability of a mineral. In doing so, three aspects have tob econsidere d : 1. The proper choice of molecular formula units enablinga compariso n of AG°el- values of minerals.
    [Show full text]
  • Clay Minerals
    CLAY MINERALS CD. Barton United States Department of Agriculture Forest Service, Aiken, South Carolina, U.S.A. A.D. Karathanasis University of Kentucky, Lexington, Kentucky, U.S.A. INTRODUCTION of soil minerals is understandable. Notwithstanding, the prevalence of silicon and oxygen in the phyllosilicate structure is logical. The SiC>4 tetrahedron is the foundation Clay minerals refers to a group of hydrous aluminosili- 2 of all silicate structures. It consists of four O ~~ ions at the cates that predominate the clay-sized (<2 |xm) fraction of apices of a regular tetrahedron coordinated to one Si4+ at soils. These minerals are similar in chemical and structural the center (Fig. 1). An interlocking array of these composition to the primary minerals that originate from tetrahedral connected at three corners in the same plane the Earth's crust; however, transformations in the by shared oxygen anions forms a hexagonal network geometric arrangement of atoms and ions within their called the tetrahedral sheet (2). When external ions bond to structures occur due to weathering. Primary minerals form the tetrahedral sheet they are coordinated to one hydroxyl at elevated temperatures and pressures, and are usually and two oxygen anion groups. An aluminum, magnesium, derived from igneous or metamorphic rocks. Inside the or iron ion typically serves as the coordinating cation and Earth these minerals are relatively stable, but transform- is surrounded by six oxygen atoms or hydroxyl groups ations may occur once exposed to the ambient conditions resulting in an eight-sided building block termed an of the Earth's surface. Although some of the most resistant octohedron (Fig.
    [Show full text]
  • 12Cl23h2o, a New Gibbsite-Based Hydrotalcite Supergroup
    minerals Article Dritsite, Li2Al4(OH)12Cl2·3H2O, a New Gibbsite-Based Hydrotalcite Supergroup Mineral Elena S. Zhitova 1,2,* , Igor V. Pekov 3, Ilya I. Chaikovskiy 4, Elena P. Chirkova 4, Vasiliy O. Yapaskurt 3, Yana V. Bychkova 3, Dmitry I. Belakovskiy 5, Nikita V. Chukanov 6, Natalia V. Zubkova 3, Sergey V. Krivovichev 1,7 and Vladimir N. Bocharov 8 1 Department of Crystallography, St. Petersburg State University, Universitetskaya nab. 7/9, St. Petersburg 199034, Russia 2 Laboratory of Mineralogy, Institute of Volcanology and Seismology, Russian Academy of Sciences, Bulvar Piypa 9, Petropavlovsk-Kamchatsky 683006, Russia 3 Faculty of Geology, Moscow State University, Vorobievy Gory, Moscow 119991, Russia 4 Mining Institute, Ural Branch of the Russian Academy of Sciences, Sibirskaya str., 78a, Perm 614007, Russia 5 Fersman Mineralogical Museum, Russian Academy of Sciences, Leninsky Prospekt 18-2, Moscow 119071, Russia 6 Institute of Problems of Chemical Physics, Russian Academy of Sciences, Akad. Semenova 1, Chernogolovka, Moscow Region 142432, Russia 7 Nanomaterials Research Centre, Kola Science Centre, Russian Academy of Sciences, Fersman Street 14, Apatity 184209, Russia 8 Resource Center Geomodel, St. Petersburg State University, Universitetskaya nab. 7/9, St. Petersburg 199034, Russia * Correspondence: [email protected]; Tel.: +7-924-587-51-91 Received: 2 August 2019; Accepted: 14 August 2019; Published: 17 August 2019 Abstract: Dritsite, ideally Li Al (OH) Cl 3H O, is a new hydrotalcite supergroup mineral formed 2 4 12 2· 2 as a result of diagenesis in the halite carnallite rock of the Verkhnekamskoe salt deposit, Perm Krai, − Russia. Dritsite forms single lamellar or tabular hexagonal crystals up to 0.25 mm across.
    [Show full text]