The Mossbauer effect has been used to measure the ferric to ferrous iron ratio in two perpendicular profiles across a 5-ft griphite crystal. No ferric iron is observed in the center of the crystal. The amount of Fe⁺³ increases rather systematically toward the margins. This increase is interpreted to have been produced by a secondary alteration caused by hydrothermal solution or weathering. These observations are in agreement with strontium isotope studies reported earlier.

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