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Limestone is a common sedimentary rock consisting mostly of the
mineral calcite (calcium carbonate, CaCO3) |
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The primary source of this
calcite are the skeletons and shells of marine
organisms. Secondary
calcite may also be deposited by supersaturated waters such as
stalagmites and stalactites. Limestone makes up approximately 10 percent
of the total volume of all sedimentary rocks. Pure limestones are white
or almost white. Because of impurities, such as
clay,
sand, organic
remains, iron oxide and other materials, many limestones exhibit
different colours, especially on weathered surfaces.
Soils reach in
limestone (calcareous
soils) are alkaline. The
particular plants adapted to live in
such a calcareous habitat are
called calciophilous plant.
Many cactus and
succulents
are
calciophilous and need some limestone grit/sand in the
potting mix. |