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- 3 A POPULAR GUIDE TO MINERALS referred; viz, the Isometric, though the various forms of this sys-tem could be derived also from the cube by replacement of its edgesor by truncation of its angles, as can, in a measure, be seen in thefigures on Plate i. The axes, assumed as lines of construction, and with referenceto which the formulae of the faces of a crystal, express the relationof those faces to these assumed axes—these axes are,
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- 3 A POPULAR GUIDE TO MINERALS referred; viz, the Isometric, though the various forms of this sys-tem could be derived also from the cube by replacement of its edgesor by truncation of its angles, as can, in a measure, be seen in thefigures on Plate i. The axes, assumed as lines of construction, and with referenceto which the formulae of the faces of a crystal, express the relationof those faces to these assumed axes—these axes are, at least,demonstrably, directions of force and accretion, in other words,there is polarity in the development of crystals. This is shown inskeleton forms of crystals, where elemental units, in the shape ofminute or small crystals, have united along lines at right angles to. FiR. 6 each other, as in the silver of Alva, Scotland, (Fig. 6), forminga skeletal frame or scaffolding for an octahedron, to be filled out;while on each line a progressive enlargemenc is noticed, the terminalcrystal forming the solid angle of the contemplated , hollow cubes of salt or hollow octahedrons of cupriteevince a predominant segregation along edges which are parallel
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmineral, bookyear1912
