DEFINITION OF THE CONCEPT "CLAY MINERAL"

A BRIEF HISTORY IS PRESENTED OF STUDIES OF THE PROPERTIES OF CLAY MINERALS. PRINCIPLE SPECIFIC FEATURES OF THE CRYSTAL CHEMISTRY OF SURFACES OF CLAY MENERALS ARE POINTED OUT BY COMPARISON WITH THOSE OF NONARGILLACEOUS MINERALS OF SIMIALR STRUCTURE. BASIC CRITERIA ARE POSTULATED FOR INCLUDING MINERALS GROUP, AND THE ESSENCES PRESENTED OF CLAY PROPERTIES OF ROCK. THE UNEQUAL ENERGY OF ADSORPTION SITES (WITH RESPECT TO CATIONS AND MOLECULES OF WATER) ON MINERAL SURFACES IS RESPONSIBLE FOR THE NATURE OF THE PROCESSES TAKING PLACE AT THE INTERFACE IN A GIVEN SYSTEM. MOST CLAY MINERALS EXHIBIT A LAMINAR CRYSTAL STRUCTURE AND A CHARACTERISTIC FEATURE IS THE ACTIVITY OF THE SURFACES OF THE CRYSTAL BASES IN ADSORPTION OF CATIONS AND WATER MOLECULES. THE ADSORPTION SITES OF THE CRYSTAL BASES OF CLAY MINERALS ARE USUALLY RELATED TO CATIONS OF ALKALI AND ALKALINE-EARTH METALS. THESE ARE THE EXCHANGE CATIONS WHICH FORM AN INTEGRAL HOLD WITH THE CRYSTAL LATTICE OF THESE MINERALS AND THEY ARE LINKED TO THE SURFACE BY BONDS OF WEAKER ENERGY, THEN THE SMALLER NUMBER OF CATIONS ABSORBED FROM THE SURROUNDING MEDIUM BY THE ADSORPTION SITES ON SURFACES OF THE CORNERS, EDGES, AND CLEAVAGE PLANES OF THE CRYSTALS, WHICH ARE BROKEN VALENCE BONDS. FOR NONARGILLACEOUS MINERALS,THE NATURAL STATE IS MACROCRYSTALLINE. IT IS PROPOSED THAT THE TERM CLAY MINERAL BE APPLIED TO CRYSTALLINE HYDROUS SILICATES, CHARACTERIZED BY THE FOLLOWING CRITERION: (1) A LAMINAR OR CHAIN-LAMINAR TYPE OF STRUCTURE, (2) A HIGH DEGREE OF DISPERSITY, (3) PREDOMINANCE OF ADSORPTION SITES FOR CATIONS AND WATER MOLECULES ON THE BASAL FACES OF THE CRYSTALS OVER SIMILAR SITES ON THE CORNERS, EDGES, AND CLEAVAGE FACES, (4) ADSORPTION SITES OF THE FIRST CATEGORY EXHIBIT LOWER ENERGY THAN THOSE OF THE SECOND, (5) SURFACE DISSOCIATION IN AN AQUEOUS MEDIUM AND THE RESULTANT FORMATION OF A LAYER OF OSMOTIC WATER AT THE MINERAL SURFACES, (6) THE PRESENCE OF A SPECIAL TYPE OF OSMOTIC WATER ON THE OUTER BASAL SURFACES OF THE CRYSTALS AND THEIR MICROAGGREGATES IN AN AQUEOUS MEDIUM, AND (7) THE MANIFESTATION OF "CLAY" PROPERTIES IN THE SYSTEM MINERALS-WATER-IONS WHEN IT CONTAINS OSMOTIC WATER OF MINERALS. THE DEGREE OF SURFACE DISSOCIATION OF CLAY MINERALS INCREASES WITH THEIR DEGREE OF HYDRATION UP TO A MOISTURE CONTENT CORRESPONDING TO MAXIMUM SWELLING OF THE CLAY, AND THEN REMAINS CONSTANT.

  • Supplemental Notes:
    • Vol 12, No 5, PP 567-575, 6 FIG, 1 TAB, 19 REF
  • Authors:
    • Kul'chitskiy, L I
  • Publication Date: 1970-5

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Filing Info

  • Accession Number: 00237891
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jul 21 1970 12:00AM