Question

In general, how does the characteristic mineral composition of a light colored igneous rock differ from that of a dark colored igneous rock?

Answer 1

Hint: The formation of igneous rocks happens, when molten rock material solidifies. A part of these rocks form underneath the Earth's surface (intrusive). Some emerge on or above the surface of the Earth (extrusive). Depending on the chemical compositions, these rocks are divided into four types: intermediate, felsic, ultramafic, and mafic.

Complete answer:
The rocks that may form as a result of the liquid crystallization are said to be igneous (molten rock). Igneous rocks are roughly classified into two types. Intrusive or plutonic igneous rocks form when magma underneath the surface of the earth crystallizes. Extrusive or volcanic rocks form at the surface of the earth from lava.The chemical composition of igneous rocks can be used to classify them.

One of the most generic classifications is based on;
- The relative abundance of felsic (feldspar and silica-quartz) minerals in this rock
- Compared to mafic (magnesium and ferrum or iron) minerals in this rock.
- Felsic minerals (quartz, K feldspar, etc.) are usually light in color
- While mafic minerals (hornblende, pyroxenes) are typically dark in color.
- The melting points of felsic minerals are the lowest, whilst mafic minerals have comparatively higher melting points.

So the real difference between the compositions of each of the colored igneous rocks are;

Light colored Igneous Rocks	Dark colored Igneous Rocks
Felsic refers to igneous rock which is normally light-colored.	Mafic refers to the category of igneous rocks that are generally dark-colored.
‘Felsic’ the name comes from its composition which consists of: 'feldspar' and 'silica-quartz'.	‘Mafic’ the name comes from its composition: ‘magnesium’ and ‘iron’(ferric).
The reason for felsic igneous rocks to be lighter in color could be because they do not contain elements which undergo oxidation easily.	The reason for mafic igneous rocks to be darker in color could be because they contain metallic elements which undergo oxidation easily (like iron).
Here the quantity of silica is higher which makes iron lower.	Alternatively there is a lower amount of silica with an overpowering amount of iron (since olivine and pyroxene compose these).

Note: The term ‘igneous' is derived from the Latin where it means ‘made of fire.'Igneous rock constitutes the majority of the earth's crust. The moon is composed of igneous rocks. These rocks also compose several mountains. Furthermore, the presence of several mountains surrounded by igneous rock indicates that the mountain is or could be a volcano.