Marble vs Limestone

Marble

Marble and limestone are calcium carbonates, CaCO3.
Marble: a metamorphic rock.
Marble forms when sedimentary limestone is heated and squeezed by natural rock-forming processes so that the grains recrystallize.
Marble is usually light colored and is composed of crystals of calcite locked together like pieces of a jigsaw puzzle.
Marble may contain colored streaks that are inclusions of non-calcite minerals.
- Iron oxide can cause yellow and brown deposits, while iron and feldspar (KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8) will create pink and red coloration.
- Serpentine creates a green hue while porphyry deposits will create a violet coloring.

Limestone: a sedimentary rock, typically composed of calcium carbonate fossils
Limestone forms when shells, sand, and mud are deposited at the bottom of oceans and lakes and over time solidify into rock.
If you look closely at a limestone, you can usually see fossil fragments (for example, bits of shell) held together by a calcite matrix.
Limestone is more porous than marble, because there are small openings between the fossil fragments.

Limestone statue of a woman, Archaic Period, early 6th century B.C., limestone, 76 cm (30 in.), the Metropolitan Museum of Art , New York City.
Venus de Milo, Alexandros of Antioch, c. 130–100 BCE, Greek, marble, 203 cm (80 in), Louvre Museum, Paris
David, Michelangelo, Italian Renaissance, c. 1504, marble, 5.17-metre (17.0 ft), Galleria dell'Accademia, Florence, Italy
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