Limestone

Limestone is calcareous sedimentary rocks formed at the bottom of lakes and seas with the accumulation of shells, bones and other calcium rich goods. It is composed of calcite (CaCO3). The organic matter upon which it settles in lakes or seas, are preserved as fossils. Over thousands and millions of years, layer after layer is built up adding weight. The heat and pressure causes chemical reaction at the bottom and the sediments turn into solid stone, the limestone.

The rock which contain more than 95% of calcium carbonate is known as high-calcium limestone. Recrystallised limestone takes good polish and is usually used as decorative and building stone.

A part of calcium molecules if being replaced by magnesium, it is known as magnesium lime stone or dolomite limestone.

Limestone that will take a polish are considered marbles by most people, but technically, if there are still shells visible or the structure is not crystalline, it is still a limestone.

Physical Properties of Limestone

Physically, Limestones are Quite impervious, Hard, Compact, fine to very fine grained calcareous rocks of sedimentary nature.

Hardness	3 to 4 on Moh's Scale
Density	2.5 to 2.7 Kg/cm3
Compressive Strength	60-170 N/mm2
Water Absorption	Less than 1%
Porosity	Quite low
Weather Impact	Resistant

Chemical Properties of Limestone

Chemically, they are calcareous rocks principally of calcic minerals with minor amounts of alumina, ferric & alkaline oxides.

Lime (CaO)	38-42%
Silica (SiO2)	15-18%
Alumina (Al2O3)	3-5%
MgO	0.5 to 3%
FeO + Fe2O3	1-1.5%
Alkalies	1-1.5%
Loss On Ignition (LOI)	30-32%

Note :- Limestone, like marble and other calcareous stones, are referred to as acid sensitive. Calcareous stones are readily dissolved in acid, therefore acidic products should not be used on limestone and marbles.

Uses of Limestone

• Flooring
• Wall cladding
• Vanity tops
• Furniture
• Cement Production
• RefiningMetals
• Blackboard chalk

Ocurrances of Limestone

Texas	Lampasas River area
India	Khasi, Jayantia and Garo Hills of Meghalaya Satna limstone belt, Madhya Pradesh
United Kingdom	United Kingdom Alston, Cumbria Stockfield, Northumberland Doncaster, South Yorkshire Moelfre, Gwynedd Ancaster, Lincolnshire Lincoln, Lincolnshire Oakham, Leicestershire Peterborough, Northamptonshire Grantham, Lincolnshire Stamford, Lincolnshire Linby, Nottinghamshire
New Zealand	Airedale Road Weston