What are the following rocks made of?

Question

What are the following rocks made of?
1) Limestone
2) Chalk
3) Marble

I know they all contain Calcium Carbonate but what else? Pecentages would be helpful

Answer 1

From my little "Rocks and Mineral" book in my school Geology days :

1) Limestone, as a rule, derived from chemical deposits of calcium carbonate and from the accumulated shells of dead organisms. However, there are also forms that result from the crystallisation of calcite. Nearly all limestones contain a little silica, partly as cryptocrystalline quartz and partly as silicate. Certain limestones are rich in silica. The puest limestone was deposited volcanically and is white.

2) Chalk is yellow-white to an intense and pure white. Its most important constituent is the remains of dead animals, many of them unicellular and microscopically small. cryptocrystalline quartz is a common impurity. Chalk is a form of calcite, a mineral which consists of calcium carbonate.

3) Marble is either recrystallised limestone or dolomite. Its colour varies from greenish and grey to white, which is the commonest form. Marbles usually occur together with iron ore and metamorphosed volcanic rocks - particularly those rich in silica. These are called leptites.

Answer 2

You ask a question that is more difficult than you might expect

For starters the three rock names or types you list do not have any specific or precise mineralogy or elemental composition associated with them.
Limestone for instance can be all calcium carbonate, but more than likely has some aragonite, dolomite etc.. in it as well as a very wide range of trace elements.
To calrify this, your question is a little bit like asking what are the following dinners made out of:
1. Hamburger at Mcdonalds
2. dinner at an expensive steakhouse
3. Dinner at a beef BBQ restaurant

Ok.. they all probably consist of beef... but there is probably a lot of other variations
ok..kind of a dumb example but

What is interesting about the rocks you list is that they tell you very different things about their history and or origin

Chalk: made almost entirely of skeltons of small marine plants called coccoliths. Interesting because there is generally little else mixed in with them, which suggests that they were deposited in deep water, far from land and over a long period of time

Limestone, this is a tough one because it is a VERY broad term. Limestone though generally is at least partially composed of shell debri and calcareous muds...the extents of each can vary wildly.

Marble, is more of a process oriented name. Marble is a metamorphosed limestone, so all the variations possible in limestone are amplified in marble...

I know I probably made this more complicated... but the real world is often more complicated

Answer 3

Limestone is made from the hard parts of small marine creatures. As they die, the soft parts decay and the hard parts (calcium) are deposited on the ocean floor. As these sediments build up and compress under their own weight and the weight of the water above, to form chalk, and with more compression, limestone. Marble is limestone that has been subjected to extreme compression and to extreme heat when it is folded deep into the earth by tectonic movement. It is eventually revealed by further movements and/or erosion. Marble is a Metamorphic Rock, he two other basic types of rock being Igneous (volcanic in origin) while limestone and chalk are sedimentary rock.

Answer 4

Limestone is made mostly of CaCO3 and may have some other minerals due to recrystallisation. Chalk contains millions of microfossils (coccoliths to be precise) which have shells themselves made of calcium compounds. Therefore chalk is a very pure organic rock. It is rich in microfossils becuase of a change in climate during the cretaceous period, that leads to a great loss of population among the coccoliths. Marble is basically metamorphosed limestone. It is metamorphosed by contact metamorphism; heat only and minimal pressure.

Answer 5

they are all calcium carbonate, which can be anything from 100% to 60% depending on impurities. the main impurity is magnesium carbonate. basically tho, it's 90%+ carbonate.

the difference between the 3 rocks
1 - coarse grained carbonate
2- fine graqined carbonate
3- metamorphosed carbonate

Answer 6

Its not that these rocks are different atomically its that there different in a larger sense.

For example chalk is a sedimentary rock that forms over millions of years from decaying materials as is limestone, but marble is chalk compressed and heated in the earth for millions of years, these rocks are called metamorphic rocks. The only difference between them is how they are made, not the proportion of atoms.

Answer 7

Chalk: mostly calcite Marble: mostly calcite Limestone: mostly calcite Malachite is a mineral, not a rock. It's formula is: Cu2CO3(OH)2, which consists of the elements: copper, oxygen, carbon and hydrogen

Answer 8

Chalk- made almost entirely of skeltons of small marine plants called coccoliths.
Limestone - composed of shell debri and calcareous muds...the extents of each can vary wildly.
Marble- is more of a process oriented name. Marble is a metamorphosed limestone

Answer 9

They are all made of calcium carbonate.
Chalk is a soft limestone.
Marble (i think) has been metamorphosed slightly. It is much harder than chalk