The original version of this flowchart was created by Mike B. --Editor
Following these steps are not absolute or infallible for finding out if the Unknown Sample in your hand is a Mineral, an Igneous Rock, a Sedimentary Rock, or a Metamorphic Rock, but these steps will work at least 95% of the time. You won't have a flowchart like this during a test, so try to remember these steps as best you can!
Start with an Unknown Sample:
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Does it have obvious planes of cleavage OR obvious fracture-patterns (cleavage in many different directions)?
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NO
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It's a Rock! Do you see mineral crystals locked together with nothing between them?
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YES
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Are the minerals in easily seen layers or shimmering or striped patterns all going in the same direction?
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NO
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Does it react to HCl?
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YES
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It's a Metamorphic Rock! (Marble)
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YES
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NO
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YES
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NO
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It's a Mineral!
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Does it react to HCl?
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It's a Foliated Metamorphic Rock!
(Slate, Phyllite, Schist, Gneiss)
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Does it have Vesicular/Porous texture?
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YES
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It's a Vesicular Igneous Rock!
(Pumice, Scoria)
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YES
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NO
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NO
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It's a Carbonate Sedimentary Rock!
(Limestone, Fossiliferous Limestone, etc).
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Is it smooth and black and easily breaks apart in your fingers?
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YES
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It's an Organic Sedimentary Rock!
(Bituminous Coal)
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Are 100% of the mineral grains identical to each other?
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YES
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It's (probably) a Non-Foliated Metamorphic Rock! (Quartzite) It could possibly be an Extrusive Igneous Rock too. (Rhyolite, Andesite, Basalt)
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NO
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NO
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It's a Non-Foliated Metamorphic Rock (Anthracite Coal)
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YES
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Is it smooth and black but seems shiny and doesn't break easily?
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NO
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Does it look like it could *maybe* be many mineral samples fused together?
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YES
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It's an Evaporite/Precipitate Sedimentary Rock! (Gypsum, Rock Salt)
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It's an Intrusive or Porphyritic Igneous Rock! (Granite, Gabbro, Diorite, Porphyritic Rhyolite, Porphyritic Andesite).
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NO
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It's a Clastic Sedimentary Rock!
(Shale, Mudstone, Sandstone, Conglomerate, Breccia)
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YES
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Does it feel muddy when you rub your finger hard against it OR does it look like sand or other small bits are all stuck together with some kind of mud or glue?
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NO
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If you look at it from the side, does it look like it has layers?
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YES
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It's a Foliated Metamorphic Rock! (Slate, Phyllite, Schist, Gneiss)
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NO
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It's probably an Igneous Rock.
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Rock & Mineral Identification Flowchart
