Browse Items (32 total)

  • Collection: (SFM) Igneous Suite -- St. Francois Mountains, Southeastern Missouri

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Hand Sample: Aphanitic, grayish-white with some patches of fine-grained grey crystals. Weathers to medium yellow-brown.

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Hand Sample: Aphanitic grey-black color. Weathers to yellow-tan and orange. Small vesicles present.

Hand Sample: Aphanitic brown-black basalt with microcrystalline inclusions of quartz and alkali feldspar. Weathers to yellow orange. Part of a dike cross cutting granite at the Cornwall Quarry.

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Hand Sample: Porphyritic orange-pink rhyolite. Dominantly potassium feldspar with some black crystals. Weathers to brown-black and yellow-brown.

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Hand Sample: Porphyritic diabase with coarse to very coarse grained subhedral pink-green plagioclase laths approximately 3cm in length set in a gray-black matrix. Inclusions of matrix present within plagioclase laths. Weathers to orange-brown.

Hand Sample: Hypocrystalline, porphyritic, diabase with subhedral plagioclase and alkali feldspar (weathered to green) crystals approximately 1cm in length. Matrix is brown-black color. Weathered to white. Intensive weathering on one side to light…

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Hand Sample: Porphyritic (or coarse-grained phaneritic) diorite with coarse-grained white plagioclase laths up to 1cm and some black mineral. Weathering to rust-orange color.

Hand Sample: Holocrystalline, phaneritic, porphyritic, diorite with quratz crystals up to 3mm in diameter set in a field of smaller light gray, and dark gray crystals. Some small oxidized pyrite crystals. Very weathered on two sides to orange yellow…

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Hand Sample: Phaneritic rhyolite with fine-grained phenocrysts of quarts, feldspar and hornblende in a brownish-red groundmass. Weathers to orange-brown.

Hand Sample: Holocystalline, phaneritic, medim-grained granitoid with subhedral grains of smoky quartz, plagioclase feldspar, potassium feldspar, and biotite. Weathering to red-yellow on some surfaces.

Hand Sample: Holocrystalline, phaneritic, medium-grained granite composed predominantly of smaller alkali feldspar crystals with larger crystals of smoky quartz, biotite, and plagioclase feldspar

Hand Sample: Holocrystalline, phaneritic, medium-grained granitoid with an abundance of alkali feldspar. Other minerals include quartz and biotite. Some chemical weathering has produced a white coating.

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Hand Sample: Holocrystalline, medium-grained phaneritic granite with smoky quartz, potassium feldspar, and biotite

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Hand Sample: Porphyritic fine-grained light-pink and black phenocrysts in a reddish-purple-brown matrix. Hospitable to grey-brown lichen.

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Hand Sample: Aphanitic, pyroclastic grey-black tuff. Conchoidal fracture pattern from a strike-point on one edge. Weathers to yellow-brown.

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Hand Sample: Holocrystalline medium-grained phaneritic granite with crystals including potassium feldspar and smokey quartz.

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Hand Sample: Phaneritic rhyolite. 10% fine-grained phenocrysts of sanidine and quartz and 90% dark-brownish-red groundmass. Weathers to brown-orange.

Hand Sample: Holocrystalline, phaneritic, fine-to-medium-grained quartz monzonite. Mineralogy includes large plagioclase laths up to 8mm in length, quartz, alkali feldspar, biotite. Very large crystals of a dark material up to 3cm in length.…

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Hand Sample: Porphyritic latite with medium-to-coarse-grained subhedral plagioclase phenocrysts in a brown-black groundmass. Thin black veins present with green margin of contact on either side.

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Hand Sample: Phaneritic granite with coarse-grained phenocrysts of smokey quartz and generally smaller crystals including potassium feldspar. Weathers to orange on one side and some light-gray material on the other.
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