The fine-grained ash groundmass contains equal proportions of scoriaceous tachylite and palagonite with basaltic lithic fragments. |
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Amygdaloidal cavities are located immediately below the uppermost scoriaceous part of the second flow, near its contact with the overlying flow. |
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On the western side of the mesa, black hornblende xenocrysts several centimeters in size are also found in a scoriaceous, agglomeratic portion of the lava flow. |
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Shoshonite nearest the contact with the overlying flow is scoriaceous and, being less weather resistant, has eroded back to form a conspicuous bench. |
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