is composed of alternating bands of light and dark silicate minerals,
Marble
Cschist
Phyllite
gneiss
The Correct Answer and Explanation is :
The correct answer is gneiss.
Gneiss is a type of metamorphic rock that is characterized by its distinctive banding or alternating layers of light and dark silicate minerals. The bands in gneiss are typically formed due to the high-grade metamorphism of pre-existing rocks under intense heat and pressure, causing the minerals to segregate into distinct layers. These bands can vary in width and can be seen on a large scale, giving the rock a foliated or layered appearance. The light bands are primarily composed of minerals like quartz and feldspar, while the dark bands are rich in minerals such as biotite, hornblende, or garnet.
Gneiss forms from the metamorphism of a variety of precursor rocks, including granite or shale, and the alternating bands of light and dark minerals are indicative of the different conditions experienced during its formation. This rock is known for its durability and aesthetic appeal, which makes it popular in construction and decorative stone applications.
Marble, schist, and phyllite are other types of metamorphic rocks, but they have different characteristics:
- Marble is a metamorphosed form of limestone and is primarily composed of calcite or dolomite. It typically does not exhibit banding but can have a crystalline texture, often with veins of different minerals.
- Schist is a metamorphic rock that features prominent foliated textures, but its mineral composition is not typically arranged in the alternating light and dark bands seen in gneiss. Schist often contains abundant mica and other minerals that give it a shiny appearance.
- Phyllite is a low-grade metamorphic rock that is finer-grained than schist. It has a silky or glossy sheen and does not display the strong banding characteristic of gneiss.
In conclusion, gneiss is the rock that displays the alternating bands of light and dark silicate minerals, making it the correct choice.