Olivine
Bowen's Reaction scale lists the order in which minerals crystallize. Olivine or ultramafic minerals are the first to crystallize. They do so at high temperatures, whereas quartz is the last to crystallize, and at low temperatures. Through Bowen's many studies, he found that the order of magma from high to low temperature is ultramafic, mafic, intermediate, and felsic. Plagioclase feldspar follows the crystallization of olivine.
Minerals like olivine and pyroxene crystallize early in Bowen's reaction series. These minerals form at high temperatures as magma cools and solidify first due to their higher melting points compared to other minerals in the series.
Minerals with higher melting points will crystallize first as the magma cools because they will solidify at higher temperatures. This process is known as fractional crystallization and helps explain the formation of different mineral layers in a cooling magma chamber.
Poikilitic texture refers to crystals, typically phenocrysts, in an igneous rock which contain small grains of other minerals. The texture is most easily observed in petrographic thin sections.
As a first approximation, the colour of igneous rocks gives an estimate of the concentration of iron in it. Very dark igneous rocks commonly a large fraction of minerals with iron as a major constituent. As those minerals are denser than most other silicate minerals occuring in igneous rocks, dark colored igenous rocks are usually denser than the ligher ones.
The first ferromagnesian mineral to crystallize is usually olivine, followed by pyroxene and amphibole. Among the feldspars, plagioclase feldspar is usually the first to crystallize, followed by potassium feldspar.
The first minerals to form when magma cools and is rich in iron, calcium, and magnesium are typically olivine, pyroxene, and/or plagioclase feldspar. These minerals have high melting points and tend to crystallize early as the magma cools.
Bowen's Reaction scale lists the order in which minerals crystallize. Olivine or ultramafic minerals are the first to crystallize. They do so at high temperatures, whereas quartz is the last to crystallize, and at low temperatures. Through Bowen's many studies, he found that the order of magma from high to low temperature is ultramafic, mafic, intermediate, and felsic. Plagioclase feldspar follows the crystallization of olivine.
crystallize first because they will solidify at higher temperatures. This process is called fractional crystallization and leads to the formation of different minerals with varying compositions and textures in the cooling magma.
quartz
quartz
The left branch of the Y-shaped arrangement consists of the discontinuous series that begins with olivine at the highest temperature and progresses through pyroxene, amphibole, and biotite as the temperature decreases. This series is discontinuous because the reaction occurs at a fixed temperature at constant pressure wherein the early-formed mineral is converted to a more stable crystal. Each mineral in the series displays a different silicate structure that exhibits increased polymerization as the temperature drops; olivine belongs to the island silicate structure type; pyroxene, the chain; amphibole, the double chain; and biotite, the sheet. On the other hand, the right branch is the continuous reaction series in which plagioclase is continuously reacting with the liquid to form a more albitic phase as the temperature decreases. In both cases, the liquid is consumed in the reaction. When the two reaction series converge at a low temperature, minerals that will not react with the remaining liquid approach eutectic crystallization. Potash feldspar, muscovite, and quartz are crystallized. The phases that are crystallized first are the common minerals that compose basalt or gabbro, like bytownite or labradorite with pyroxene and minor amounts of olivine. Andesite or diorite minerals, such as andesine with either pyroxene or amphibole, crystallize next and are followed by orthoclase and quartz, which are the essential constituents of rhyolite or granite. A basaltic liquid at the top of the Y can descend to the bottom of the series to crystallize quartz only if the earlier reactions are prevented. As demonstrated above, complete reactions between early-formed minerals and the liquid depletes the supply of the liquid, thereby curtailing the progression down the series. One means by which basaltic magma can be transformed to rocks lower in the series is by fractional crystallization. In this process, the early-formed minerals are removed from the liquid by gravity (such minerals as olivine and pyroxene are denser than the liquid from which they crystallized), and so unreacted liquid remains later in the series.
Minerals like olivine and pyroxene crystallize early in Bowen's reaction series. These minerals form at high temperatures as magma cools and solidify first due to their higher melting points compared to other minerals in the series.
They form more euhedral shapes because they are the first to crystallize, and don't have to compete for room.
If a magma of higher temperature cools down, certain minerals solidify first. Eventually, those minerals that remain liquid at the lowest temperatures solidify the latest. The rock that is then formed is Granite (if it's intrusive), or Rhyolite (if it's extrusive)
The mineral that crystallizes first from magma is olivine. Olivine has a relatively high melting temperature compared to other minerals, so it is among the first to solidify as magma cools and begins to solidify.
Wendell Stanley