S-type granites are a category of granites first proposed in 1974.[1] They are recognized by a specific set of mineralogical, geochemical, textural, and isotopic characteristics. S-type granites are over-saturated in aluminium, with an ASI index greater than 1.1 where ASI = Al2O3 / (CaO + Na2O +K2O) in mol percent;[1][2][3] petrographic features are representative of the chemical composition of the initial magma as originally put forth by Chappell and White are summarized in their table 1.[1][4]