[Ans] The colour of soil which is formed by basalt?

Step 1 : Introduction to the question "the colour of soil which is formed by basalt"

By definition, basalt is an aphanitic (fine-grained) igneous rock with generally 45-55% silica (SiO2) and less than 10% feldspathoid by volume, and where at least 65% of the rock is feldspar in the form of plagioclase. It is the most common volcanic rock type on Earth

Step 2 : Answer to the question "the colour of soil which is formed by basalt?"

Basalt is usually grey to black in colour, but rapidly weathers to brown or rust-red due to oxidation of its mafic (iron-rich) minerals into hematite and other iron oxides and hydroxides. Although usually characterized as "dark", basaltic rocks exhibit a wide range of shading due to regional geochemical processes. Due to weathering or high concentrations of plagioclase, some basalts can be quite light-coloured, superficially resembling andesite to untrained eyes.

Step 3 : Other interesting facts related to the question "the colour of soil which is formed by basalt"

The word "basalt" is ultimately derived from Late Latin basalte. Tholeiitic basalt is relatively rich in silica and poor in sodium. High-alumina basalt may be silica-undersaturated or -oversaturated . Alkali basalt is relatively poor in silica and rich in sodium. On Earth, most basalt magmas have formed by decompression melting of the mantle.