Biochemical sedimentary rocks are made of either shell or plant fragments. The shell fragments may be large and well cemented, large and poorly cemented, or the shell fragments may be very small and not readily recognizable. The most reliable test is to see if it reacts with hydrochloric acid. If your sample reacts with acid, it is composed of shell fragments. If it does not react, it may be composed of plant material.
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Visible fossils, very well cemented, reacts with acid |
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Visible fossils, poorly cemented and very porous, reacts with acid |
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Fossils not readily visible, very dense and often uniform in color, reacts with acid |
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Fossils not readily visible, chalky white, earthy appearance, reacts with acid |
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| No apparent fossils. Possibly some imprints of plant material. Generally dark to black in color, does not react with acid | (CLICK HERE) |
| BACK TO STEP 1|
| SEDIMENTARY ROCK TEXTURES |
SEDIMENTARY ROCK TYPES |
SEDIMENTARY ROCK CLASSIFICATION |