Generally, igneous rocks that are low in silica are dark relative to those that are high in silica. This tendency is largely the result of rocks low in silica having increased iron. Iron minerals tend to adsorb significant amounts of the visible spectrum and hence appear dark. I want to emphasize that this is a general tendency and there are exeptions -- obsidian which is very high in silica is typically a dark to black rock and a special igneous rock call carbonatite is very light in color but has little silica.
Light-coloured igneous rocks, such as granite, have a higher silica content and lower iron and magnesium than darker ones, such as basalt. Since iron and magnesium are very dense minerals, this makes darker igneous rocks more dense than lighter ones.
Dense. Light colored igneous rocks have lower density compared to dark colored igneous rocks due to their higher silica content, which results in slower cooling and the formation of larger crystals.
The igneous rock you are referring to is basalt. It is a fine-grained, dense, and dark-colored rock that forms from low-silica magma rich in iron and magnesium.
They are not low in silicate minerals. They are still primarily composed of them. However, the amount of silica in them is lower than in the lighter-colored rocks. The lightest igneous rocks (felsic) are at least 70% silica while the dark ones (mafic) are between 45% and 52% silica. Silica content below 45% is deemed ultramafic.
Light colored igneous rock is called felsic, and is high in quartz, muscovite mica, and orthoclase feldsparcontent. Dark colored igneous rock is called mafic, and contains a lesser amount of silica along with olivine, pyroxene, amphibole, biotite mica, and plagioclase feldspar.
Mafic igneous rocks, like basalt, are dark colored and low in silica.
Mafic igneous rocks, like basalt, are dark colored and low in silica.
Basalt is a dark-colored, low-silica igneous rock commonly found as a result of volcanic activity. Its composition typically contains around 50% silica, making it relatively low in silica compared to other igneous rocks like granite.
Light-coloured igneous rocks, such as granite, have a higher silica content and lower iron and magnesium than darker ones, such as basalt. Since iron and magnesium are very dense minerals, this makes darker igneous rocks more dense than lighter ones.
Normally, light colored igneous rocks are less dense compared to dark colored igneous rocks. This is because the light colored rocks have a less iron in them.
Dense. Light colored igneous rocks have lower density compared to dark colored igneous rocks due to their higher silica content, which results in slower cooling and the formation of larger crystals.
Normally, light colored igneous rocks are less dense compared to dark colored igneous rocks. This is because the light colored rocks have a less iron in them.
less dense
Granite has more silica than basalt. Granite is a light-colored, coarse-grained igneous rock made up of quartz, feldspar, and mica, which are minerals rich in silica. Basalt, on the other hand, is a dark-colored, fine-grained igneous rock with lower silica content compared to granite.
The igneous rock you are referring to is basalt. It is a fine-grained, dense, and dark-colored rock that forms from low-silica magma rich in iron and magnesium.
They are not low in silicate minerals. They are still primarily composed of them. However, the amount of silica in them is lower than in the lighter-colored rocks. The lightest igneous rocks (felsic) are at least 70% silica while the dark ones (mafic) are between 45% and 52% silica. Silica content below 45% is deemed ultramafic.
Intermediate rocks contain roughly equal amounts of dark- and light-colored minerals. Igneous rock containing 56-65 percent silica.