Elements of mineralogy, crystallography and blowpipe analysis from a practical standpoint .. . te planes or differ-ent portions may each be so split parallel to its own set of masses which are not opaque if examined by polarizedlight, as explained later, produce effects upon the light entirelydifferent from those produced by a substance with indefinitely ar-ranged particles, and in opaques masses the regular structure maybe proved by other physical tests. Massive and Amorphous. All masses which do not show definite crystal faces are said tobe massive, whether crystalline in stru
Elements of mineralogy, crystallography and blowpipe analysis from a practical standpoint .. . te planes or differ-ent portions may each be so split parallel to its own set of masses which are not opaque if examined by polarizedlight, as explained later, produce effects upon the light entirelydifferent from those produced by a substance with indefinitely ar-ranged particles, and in opaques masses the regular structure maybe proved by other physical tests. Massive and Amorphous. All masses which do not show definite crystal faces are said tobe massive, whether crystalline in structure or |not. If cleavage,polarized light and other tests fail to prove any crystalline struc-ture, the mineral is said to be amorphous. The number of min-erals accepted as amorphous is exceedingly small, but of minerals which may, from rapid cooling orother cause, be apparently amorphous. Columnar Structure. The structure is said to be columnar when the imperfectlyformed crystals are relatively long in one direction and 322. Fig. 323. Fig.
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