Final answer:
The metamorphic rock formed from sandstone is quartzite. Quartzite results from the recrystallization of sandstone's quartz grains under high pressure and temperature. This rock is hard, does not react to acid, and can take on various colors.
Step-by-step explanation:
Metamorphic rocks are a major category of rocks in the Earth's crust, distinguished by the transformation they undergo due to various geological processes. When sedimentary, igneous, or even other metamorphic rocks are exposed to high temperatures and pressures, they undergo physical, and sometimes chemical alterations, resulting in metamorphic rocks with new mineral compositions and textures.
The specific metamorphic rock formed from sandstone is quartzite. Sandstone made up of sand grains that are primarily quartz, is transformed into quartzite through the process of metamorphism. During this transformation, the individual quartz grains recrystallize and the rock becomes much harder and more compact.
The degree of heating and pressure, along with the amount of time these forces are applied, determines the characteristics of the resulting quartzite. Notably, quartzite's hardness (on the Mohs scale) is 7, and it does not react with acid, which distinguishes it from rocks like marble. Quartzite can appear in various colors, and in some cases, the original texture of the sandstone, with visible individual grains, is preserved.
These metamorphic processes commonly occur at tectonic boundaries or areas of significant geological activity where rocks are buried deeply and subjected to the Earth's geothermal gradient. These conditions are particularly prevalent in mountain belts, where the pressure from tectonic forces and the heat from the Earth's interior are greatest.
The process of metamorphism, including the transition from sandstone to quartzite, is an essential part of the rock cycle, which describes the transformation of rocks through various geological stages and forms a continuous loop of rock formation and reformation.