A popular guide to minerals : with chapters on the Bement Collection of minerals in the American Museum of Natural History, and the development of mineralogy . Fig. 165 Fig. 166 38 A POPULAR GUIDE TO MINERALS prism; Fig. i6i, Basal pinacoid, two pyramids, (proto and deutero),twc prisms (proto and deutero) ; Fig. 162, Three hexagonal pyra-mids, hexagonal prism; Fig. 163, Dihexagonal pyramid; Fig. 164,Dihexagonal prism; Fig. 165, Hexagonal pyramid, dihexagonalpyramid, two hexagonal prisms; Fig. 166, Summit of crystal, seriesof successive dihexagonal and hexagonal pyramids. (Note: thepupil
A popular guide to minerals : with chapters on the Bement Collection of minerals in the American Museum of Natural History, and the development of mineralogy . Fig. 165 Fig. 166 38 A POPULAR GUIDE TO MINERALS prism; Fig. i6i, Basal pinacoid, two pyramids, (proto and deutero),twc prisms (proto and deutero) ; Fig. 162, Three hexagonal pyra-mids, hexagonal prism; Fig. 163, Dihexagonal pyramid; Fig. 164,Dihexagonal prism; Fig. 165, Hexagonal pyramid, dihexagonalpyramid, two hexagonal prisms; Fig. 166, Summit of crystal, seriesof successive dihexagonal and hexagonal pyramids. (Note: thepupil should take Plate 8, and without mentioning the forms re-peat the symbols for each. The teacher should, in this system, il-lustrate briefly the use of formulae with four symbols, for whichpurpose, the following paragraphs will prove helpful; Weiss indi-cated in the hexagonal system the half of the vertical axis of theground form by c, the three equal half lateral axes by a. Everyface of the ground form (protopyramid) cuts the vertical axis,two of the lateral axes, at equal distances from the former, and isparallel to the third; its symbol is consequent
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmineral, bookyear1912
