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  • 館藏編號:NTUG010-T300043
  • 題名:Igneous Rocks
  • 作者:阮維周
  • 藏品形式:稿本
  • 尺寸:210X297(mm)
  • 簡述:P.41
  • 內容:

    P.41 Longulites: globulites coalescing in chainlike lines. Trichites: long, thin, dark, hairlike bodies, frequently radiating in curved lines frome a center. Clavalite Spiculite Scopulite: tree-like bodies. (2) Microlites. - They are transparent small crystals, with or without external form, colored or colorless, and can be seen only microscopically, usually in irregular form, may or may not be determinable. (3) Skeleton crystals. - They show crystallographically symmetrical or parallel arrangement, and have grown in certain direction, generally of microscopic size. (4) Spherulite. - It is composed of more or less spheroidal, concentrical layers and arranged radially resulting from the inter-growth of feldspar and quartz in acid rocks. It is with different sizes, sometimes may only be visible under microscope but sometimes ten feet in diameter. When under crossed nickel, it resembles uniaxial interference figure. Mineral constituents. (1) Primary mineral, directly produced from magma a. Essential or chief constituents b. Accessary mineral i) Minor accessories (usual minerals present in small amounts). ii) Auxiliary minerals - the minerals of small amount bear peculiar interests, as the presence of tourmaline in granite. (2) Secondary - caused by a. Addition of material, as tourmaline, topaz in granite. b. Replacement, as kaolin, chlorite, epidote, amphibole, calcite. c. Weathering, as calcite, limonite, and hydrous aluminum - 14- -