In what type of rock are fossils made of?
Limestone is a sedimentary rock made almost entirely of fossils. Fossils are the remains of ancient plants and animals, like an imprint in a rock or actual bones and shells that have turned into rock. Fossils are found in sedimentary rocks and hold the clues to life on Earth long ago.
How do you know if a rock is a fossil?
Mostly, however, heavy and lightly colored objects are rocks, like flint. Paleontologists also examine the surfaces of potential fossils. If they are smooth and do not have any real texture, they are probably rocks. Even if it is shaped like a bone, if it does not have the right texture then it is probably a rock.
Why are fossils made of rock?
After an animal dies, the soft parts of its body decompose leaving the hard parts, like the skeleton, behind. This becomes buried by small particles of rock called sediment. Minerals in the water replace the bone, leaving a rock replica of the original bone called a fossil.
Fossils are prehistoric hard rock remains or traces of plants or animals preserved in sedimentary rocks. Usually fossils are preserved by being buried underneath multiple layers of sand of mud. The sand and mud turn into sedimentary rock when under tremendous pressure.
Trace fossils are formed when an organism makes a mark in mud or sand. The sediment dries and hardens. It is covered by a new layer of sediment. As the sediment turns to rock through compaction and cementation, the remnant becomes fossilized.
Fossils form in five ways: preservation of original remains, permineralization, molds and casts, replacement, and compression.
Earth contains three types of rocks: metamorphic, igneous and sedimentary. With rare exceptions, metamorphic and igneous rocks undergo too much heat and pressure to preserve fossils. So most fossils are found in sedimentary rocks, where gentler pressure and lower temperature allows preservation of past life-forms.
Metamorphic rocks started out as some other type of rock, but have been substantially changed from their original igneous, sedimentary, or earlier metamorphic form. Metamorphic rocks form when rocks are subjected to high heat, high pressure, hot mineral-rich fluids or, more commonly, some combination of these factors.
The porous nature of some fossil bones will cause it to slightly stick to your tongue if you lick it, though you might want to have a glass of water handy if you feel compelled to try this.
The organic parts of the bone, like blood cells, collagen (a protein), and fat, eventually break down. But the inorganic parts of the bone, or the parts made from minerals like calcium, have more staying power. Over the course of millions of years, the sediment around these reinforced bones becomes sedimentary rock.