Basalt is a volcanic rock that is rich in minerals. It primarily consists of the following minerals:

1. Silicon dioxide (SiO2): This is the most abundant mineral in basalt and gives it its dark gray to black color.

2. Aluminum oxide (Al2O3): This mineral is responsible for basalt’s light gray to white color and its vitreous nature.

3. Iron oxide (FeO): This mineral gives basalt its red color and is present in varying amounts depending on the volcanic process.

4. Calcium oxide (CaO): This mineral is also present in varying amounts and contributes to the overall composition of basalt.

5. Magnesium oxide (MgO): This mineral is also found in basalt and plays a role in its composition.

6. Potassium feldspar (K-feldspar): This mineral is present in trace amounts and contributes to basalt’s vitreous nature.

7. Orthoclase (K-feldspar): This mineral is present in trace amounts and contributes to basalt’s vitreous nature.

These minerals are combined in varying proport ions to form basalt, which is a dense, hard, and felsic rock.

When limestone undergoes metamorphism and transforms into marble, several changes occur. This process is known as metamorphism, and it involves recrystallization of the original minerals in the limestone. Here’s what happens:

1. Recrystallization: The calcite crystals in limestone are typically small and randomly oriented. During metamorphism, these crystals recrystallize, growing larger and developing a more uniform and interlocking texture.

2. Mineral Change: The main mineral in limestone is calcite (calcium carbonate). Through metamorphism, calcite recrystallizes into larger crystals of calcite or, in some cases, can even be transformed into other minerals like dolomite.

3. Texture: The texture of limestone is often granular, but in marble, it becomes more crystalline and can exhibit a variety of patterns, including veining and color variations.

4. Hardness: Marble is generally harder than limestone due to the recrystallization process, which results in a denser and more tightly packed structure.

5. Color Changes: While limestone is often light-colored, marble can exhibit a broader range of colors depending on the impurities present during metamorphism. These impurities may introduce shades of gray, green, pink, or other hues.

6. Loss of Fossils: Limestone often contains fossils, but these are typically lost during the metamorphic process as the original structure is obliterated.

Marble is prized for its aesthetic qualities and is commonly used in sculpture and as a building material for flooring and countertops due to its durability and attractive appearance.