I have been on a hiking trip lately (trying to find some potential fossil sites) and i have collected some rocks, i would like you to help me identify them.

Rock 1: (i think it's limestone) enter image description here

enter image description here

Rock 2: enter image description here

Rock 3: enter image description here

locations: Rock 1 : https://goo.gl/maps/zAFeenN5hKD2 Rocks 2 & 3: https://goo.gl/maps/Ry1mqmv5AYo

Performed the nail test on the first rock, result: no effect on the rock.


closed as off-topic by Jan Doggen, uhoh, Erik, Fred, Gimelist Aug 28 at 10:12

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Rock 1 probably a limestone, but check the hardness. Rock 2 probably a sandstone, but impossible to be sure without more detailed examination. The white flecks in this case seem to be a weathering feature. In some sandstones there are grains of feldspar which weather to create white-ish grains, in which case it is most probably a variety called arkose.

When you are checking out the rocks in an unfamiliar territory may I suggest three routine geologists habits.

  1. Always carry a small tough dropper bottle of dilute hydrochloric acid. 5 or 10 mls is quite sufficient - you only need one drop per test. On any fresh rock surface add a drop of acid. If it fizzes, it is limestone.
  2. Test the hardness by trying to scratch the iron of your rock hammer with a chip of unweathered rock. If it scratches then it is very likely silica. If it doesn't scratch, then it is something soft like a limestone or other soft sediment.
  3. Always carry a X10 or x15 hand lens to check out the rock texture. Is it interlocking crystals? Is there porosity? Is the matrix of the same material as the grains? Also, since you seem to be interested in palaeontology, are there microfossils?

Then you will be in a much better position to identify your rock. But in the case of igneous or metamorphic rocks you really need a petrologic microscope, which is expensive and needs professional guidance on how to use correctly. Looking at the geological map of Morocco, the area you chose looks quite complex, with both igneous and sedimentary crystalline basement overlain by a wide range of Paleozoic sedimentary cover - and all infused by later mineralization, so expect the unexpected!

  • $\begingroup$ thank you very much sir for the precious informations and advices. $\endgroup$ – cascadox Oct 6 '16 at 7:51

Given the hardness and the appearance, I think 1 and 2 are quartzite. Rock 3 may be too. Brief Google search suggests that is generally consistent with the Atlas Mountains.

  • $\begingroup$ yes i did the vinegar test on Rock1 no reaction at all, which means that it's not limestone $\endgroup$ – cascadox Oct 14 '16 at 11:06

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