Elements of mineralogy, crystallography and blowpipe analysis from a practical standpoint .. . Arborescent or Dendritic.—Branching like a tree as in 313, or pyrolusite. Fig. CHARACTERS OF MINERALS. 145 Radiating.—Diverging from a common center, sometimes form-ing nearly complete spheres, as in pectolite from Paterson, More frequently forming partialspheres, as shown in wavellite. Fig. 553, fig. 332. or pectolite of Bergen Hill, Fig. 602. Drusy.—Closely covered with minutecrystals, giving a rough surface like sand-paper. Geode.—A hollow nodule lined withcrystals, as i
Elements of mineralogy, crystallography and blowpipe analysis from a practical standpoint .. . Arborescent or Dendritic.—Branching like a tree as in 313, or pyrolusite. Fig. CHARACTERS OF MINERALS. 145 Radiating.—Diverging from a common center, sometimes form-ing nearly complete spheres, as in pectolite from Paterson, More frequently forming partialspheres, as shown in wavellite. Fig. 553, fig. 332. or pectolite of Bergen Hill, Fig. 602. Drusy.—Closely covered with minutecrystals, giving a rough surface like sand-paper. Geode.—A hollow nodule lined withcrystals, as in the quartz geode, Fig. 332. Incrustation.—A coating or crust. HARDNESS. The resistance of a smooth plane surface to abrasion is calledits hardness, and is commonly recorded * in terms of a scale often common minerals selected by Mohs : 1. Talc, laminated. 6. Orthoclase, white cleavable. 2. Gypsum, crystallized. 7. Quartz, transparent. 3. Calcite, transparent. 8. Topaz, transparent. 4. Fluorite, crystalline. 9. Sapphire, cleavable. 5. Apatite, transparent. 10. Diamond. The following scale of Chapman gives about the same results : 1. Feels soft and greasy and is easily scratch
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