Metasomatic limestone

Metasomatic limestone is one where the original character of the deposit has been modified by the intrusion of secondary impurities. 

Ruby crystals with a similar texture are found at a contact metasomatic deposit in Myanmar, and are called trapiche rubies. Sapphires with similar textures are also known. Trapiche ruby crystals occur sporadically in marble formed by contact metasomatism due to the intrusion of a granitic magma into Mg-containing limestone. Trapiche sapphire is also formed by the contact metasomatism of Al-rich sedimentary rocks. 

Zhabin, A.G., Samsonova, N.S., Chuchua, I.B. et al. (1990) Ore-bearing metasomatically altered limestones of the black shale association. International Geology Review, 32(11), 1145-55. 

Contact metasomatic Scheelite Hydrothermal liquid invades limestone, causing a violent reaction of the acidic liquid and the limestone. Close proximity with the intrusive. Formation of huge amounts of Ca-silicates (scarn or tactite). Majority of the tungsten deposits. 

Metasomatic dolomitization is a common process, which actively affects the composition of both rocks and ground water. Three major types of dolomite are distinguished primary, precipitated together with the rock, secondary in the form of cement and the third one at dolomitization of limestones. In the latter case it forms due to the substitution of Mg instead of Ca. Because of this the very substitution process is considered as a number of sequential reactions of dissolution and precipitation. However, total substitution of dolomite instead of calcite is rare. Usually form limestones at various dolomitization stages (magnesian calcite, protodolomite). In its substance this is isomorphism of cations with the same valence, which may be presented by equation... 

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