Limestone, pretty on the beach or anywhere else
Limestone, used in buildings and cement, is a common name for the mineral calcite (calcium carbonate, CaCO3). It crystallizes in a variety of environments, and can be found around the world.
Limestone Formation
Limestone is a chemical sedimentary rock. This means that instead of being compacted and cemented, it is formed from chemical crystallization. Limestone most commonly forms via biochemical processes.
Limestone can also form from aragonite, a mineral with the same chemical make up, but different arrangement.
Marble Formation
When conditions are right, limestone can crystallize into marble, a non-foliated (non-layered) metamorphic rock (metamorphosis meaning that heat and pressure are applied to the rock without melting it). Marble is more dense and hard than the limestone it crystallized from.
Coloration
Pure limestone is white, as is the marble that comes from it. If limestone has impurities, the marble that crystallizes from it can range in color from black, green, gray or pink, depending on the impurities. Also, other, separate minerals in the limestone can be included in the marble.
Considerations
Different types of limestone exist, with each type depending on what gets mixed in during the formation process. When limestone crystallizes into marble, the type of marble formed depends on the type of limestone it comes from.
When the limestone that crystallizes into marble is inter-layered with shale, it will form foliated marble.
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