Naturally deformed and work-hardened sphalerite and galena have been experimentally recrystallized and the effects of this process on microhardnesses have been studied in detail. Specifically, the hardnesses of recrystallized material on one hand, and of the remaining unrecrystallized material on the other, have been followed separately from the onset of recrystallization and until this process was complete.For both minerals the effects of recrystallization were (1) an initial sharp fall in hardness where the material recrystallized (2) a lesser but still obvious fall in hardness of the remaining unrecrystallized material, indicating a period of incipient ordering prior to visible recrystallization (3) a hardening--"secondary hardening"--of recrystallized material as recrystallization proceeded. Secondary hardening of galena may yield a hardness greater than that of the initial work-hardened state. This may however, be a recrystallization preferred orientation effect, and therefore apparent only.The two minerals commence recrystallization somewhat differently. Sphalerite recrystallizes by apparently random nucleation of small strain-free grains within the body of individual original strained grains, whereas the new grains of galena grow from subgrains or by outgrowth of whole grains forming part of the original strained polycrystalline aggregate. Growth of new sphalerite grains is accompanied by the development of numerous twins.

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