Kivikivennäiset

Kivikivennäiset, or rock-forming minerals, are the minerals that occur most commonly in rocks and are used to describe, classify, and interpret rocks in geology. They form the bulk of igneous, metamorphic, and sedimentary rocks. Most kivikivennäiset are silicate minerals, including feldspars (plagioclase and potassium feldspar), quartz, pyroxenes, amphiboles, micas (biotite and muscovite) and olivine. Non-silicate rock-forming minerals also occur, notably carbonate minerals such as calcite and dolomite, as well as certain oxides and sulfides in specific rock types.

In a rock, some minerals are essential components that define the rock type, while others appear in smaller amounts as accessories. Silicate minerals are often grouped by crystal structure and chemistry into felsic, intermediate, mafic, and ultramafic families, a distinction that typically corresponds with characteristic rock types: felsic rocks like granite and rhyolite are rich in feldspar and quartz; intermediate rocks such as diorite and andesite; mafic rocks like basalt and gabbro; ultramafic rocks such as peridotite.

Formation and occurrence: rock-forming minerals crystallize from cooling magma, form or recrystallize during metamorphism, or precipitate and diagenetically alter in sedimentary environments. Their stability depends on pressure, temperature and chemical conditions, which in turn record the geological history of the crust.

Importance: the study of kivikivennäiset provides essential information about a rock’s origin, crustal composition and tectonic history, and underpins petrology, mineral exploration and resource assessment.