Positive and negative tetrahedrons

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“If a positive and negative tetrahedron occured together with equal development, the resulting crystal could not be distinguished from an octahedron, unless, as is usually the case, the faces of the two forms showed different lusters, etchings, or striations that would serve to differentiate them.” — Ford, 1912




William E. Ford Dana's Manual of Mineralogy (New York: John Wiley and Sons, Inc, 1912) 28


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