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A highly porphyritic rhyolite rock

Porphyritic Rhyolite Composition and Uses

Porphyritic rhyolite has large, well-formed crystals, mostly alkali feldspar, plagioclase, quartz, and less often hornblende, pyroxene, or mica in a

Categories Rocks
Porphyritic basalt rock

Porphyritic Basalt Composition and Uses

Porphyritic basalt rocks have large, well-formed grains of calcic plagioclase, augite, olivine, and sometimes hornblende in fine-grained dark-gray to black

Categories Rocks
Porphyritic granite rock

Porphyritic Granite Composition and Uses  

Porphyritic granite has large, well-formed white or pink alkali feldspar and sometimes quartz, biotite, or plagioclase in a finer but

Categories Rocks
Porphyritic gabbro rock

Porphyritic Gabbro Formation and Uses

Porphyritic gabbro has large, well-formed crystals of mostly calcic-plagioclase and sometimes augite, rarely olivine or other mafic minerals set in

Categories Rocks
Porphyritic diorite

Porphyritic Diorite Rock Formation and Uses

Porphyritic diorite rocks have large, well-formed mineral grains of feldspar and sometimes hornblende, pyroxene, or biotite set in a finer-grained

Categories Rocks
Porphyritic trachyte rock

Porphyritic Trachyte Composition and Formation

Porphyritic trachyte rocks have large, well-formed sanidine, plagioclase, and sometimes amphibole, biotite, or pyroxene crystals in a fine-grained matrix. The

Categories Rocks
Porphyritic phonolite with vesicles

Porphyritic Phonolite Formation and Uses

Porphyritic phonolite or phonolite porphyry has well-formed, large leucite, nepheline, and alkali feldspar crystals in a fine-grained matrix. The larger

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Red, Purple or Roman Imperial Porphyry rock

Purple, Red, or Roman Imperial Porphyry

Purple, red, or Roman Imperial porphyry refers to reddish to purplish porphyritic rocks highly-priced during the antiquity age by Romans

Categories Rocks
How to break, crack or open a geode - half cut

How to Crack, Break or Open a Geode Like a Pro

Would you like to know how to open a geode? The common ways are smashing it, using a crack hammer

Categories Rocks
Geode in Illinois from Lower Warsaw Formation in Hancock County - Mississippian Age

Where to Hunt for Geodes in Illinois

The best places to find geodes in Illinois are Warsaw, Hamilton, and Nauvoo, which are areas in western Illinois that

Categories Rocks
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