On this page is some basic help with rock identification.
First, decide whether the rock you have picked up is a
sedimentary, metamorphic, or igneous rock.
An igneous rock
has got an arrangement of mineral
crystals. It has got no foliation, and no fossils.
Granite - a typical igneous rock with interlocked mineral
identified by visible sedimentary layers. But not all sedimentary rocks
have sedimentary layers.
They do, however, have a special look - fine-grained ones have a very
homogenous structure, others contain larger pebbles or fossils. They are not foliated. Sedimentary rocks can be quite
weak, you can try its hardness by hitting it with a hammer.
A typical, "sandy" sedimentary rock with fossil.
A metamorphic rock is
If it's not, it is still different from igneous rocks because it does
not have mineral crystals; and it differs from sedimentaries because it
lacks bedding layers, fossils, and the sandy, homogenous structure.
A typical "shisty" (layered/foliated) metamorphic rock.
Identification - Second
Once you know what type of rock it is, establish whether it is coarse,
medium or fine grained. A rock is coarse-grained
if you can see its grains with your bare eyes. With medium-grained
rocks, you need a hand lens to see the grains separately. And with a fine-grained rock
you need a microscope.
Identification - Third
If you rock was an igneous
rock, look at its colour.
If you rock was a sedimentary
rock, look at what minerals you find in the rock.
salt, Rock Gypsum
Chert, Coal, Clay, Amber
If you rock was a metamorphic
rock, look at whether it is foliated or not.