Limestone rock

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Limestone rock is primarily composed of calcium carbonate and has many uses in NZ, for example in fertiliser production and 'shingle' paving. 

Sedimentary: Forms from accumulated shell, corals and other organic sediments (therefore technically an 'organic sedimentary' rock).

Source location: Canterbury.

Sizes: Choose from dropdown menu either Shelf specimen (300–800g), or Hand specimen (less than 300g)

Note: Images are examples of specimens only. Sizes and shapes will vary.

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A sedimentary rock primarily composed of calcium carbonate. It forms from the accumulation of shell, coral, and other organic remains, as well as the precipitation of minerals from water.


Organic sedimentary.

Physical properties of limestone

  • Colour: Can exhibit various colours, including white, cream, beige, grey, or yellow.
  • Lustre: Often has a dull lustre.
  • Hardness: Hardness ranging from 3 to 4 on the Mohs scale, making it relatively soft and susceptible to scratching.
  • Density: Ranges from 2.3 to 2.7 grams per cubic centimetre.
  • Cleavage: Has poor to fair cleavage, breaking with irregular or shell-like fragments.

General properties of limestone

  • Fossil Content: Often contains fossilised remains of marine organisms, such as shells, corals, and algae.
  • Porosity: Generally porous, allowing it to absorb and hold water.
  • Solubility: Soluble in water, particularly in acidic water, which can lead to the formation of caves and sinkholes.
  • Formation: Forms in marine environments, as well as in freshwater lakes and caves through precipitation.
  • Reaction to Acid: Reacts with acid, e.g. white vinegar, producing carbon dioxide gas and effervescence.

Uses of limestone in New Zealand and worldwide

  • Construction: Used as a construction material for buildings, walls, facades, and paving due to its durability and aesthetic appeal, for example Ōamaru Stone.
  • Lime Production: Heated to produce lime, which is used in cement, mortar, and other construction materials.
  • Agricultural Soil Amendment: Ground limestone is used as a soil amendment to neutralise acidity and provide essential nutrients to crops.
  • Flux in Metallurgy: Acts as a flux in the smelting process, aiding in the removal of impurities during metal production.
  • Dimension Stone: Cut and shaped into slabs or blocks for use in countertops, flooring, and decorative elements.
  • Chemical Industry: Used in the production of chemicals, such as calcium carbonate, calcium oxide, and calcium hydroxide.
  • Environmental Applications: Used for flue gas desulfurisation in power plants and as a neutralising agent in acid mine drainage.