Pyroxenite vs. Serpentinite

Attribute	Pyroxenite	Serpentinite
Composition	Rich in pyroxene minerals	Rich in serpentine minerals
Color	Dark green to black	Green to gray
Texture	Coarse-grained	Fine-grained
Formation	Forms from the crystallization of magma	Forms from the alteration of ultramafic rocks

Composition

Pyroxenite is a type of ultramafic rock that is composed primarily of pyroxene minerals such as augite, diopside, and enstatite. These minerals give pyroxenite its characteristic dark green to black color. On the other hand, serpentinite is a metamorphic rock that is primarily composed of serpentine minerals such as antigorite, chrysotile, and lizardite. Serpentinite is typically green in color and has a waxy luster.

Texture

Pyroxenite has a coarse-grained texture due to its formation deep within the Earth's mantle. The large crystals of pyroxene minerals are easily visible to the naked eye. In contrast, serpentinite has a more compact and fine-grained texture. The serpentine minerals in serpentinite are intergrown and tightly packed together, giving the rock a smooth appearance.

Formation

Pyroxenite is formed through the crystallization of magma deep within the Earth's mantle. As magma cools and solidifies, pyroxene minerals crystallize and form pyroxenite rocks. Serpentinite, on the other hand, is formed through the metamorphism of ultramafic rocks such as peridotite. When peridotite comes into contact with water, the minerals in the rock undergo a chemical reaction that transforms them into serpentine minerals, resulting in the formation of serpentinite.

Uses

Pyroxenite is commonly used as a decorative stone in construction and landscaping due to its dark color and attractive appearance. It is also used as a source of magnesium and other minerals. Serpentinite, on the other hand, is used in a variety of applications such as building materials, countertops, and carvings. It is also used as a source of asbestos, although this use has declined due to health concerns associated with asbestos exposure.

Geological Significance

Pyroxenite is an important rock type in the Earth's mantle and plays a role in the formation of other rocks such as basalt and gabbro. It is also associated with the formation of diamonds in kimberlite pipes. Serpentinite, on the other hand, is important in the process of subduction, where oceanic crust is forced beneath continental crust. The hydration of ultramafic rocks such as peridotite to form serpentinite plays a key role in the recycling of elements in the Earth's crust.

Location

Pyroxenite is found in a variety of geological settings, including ophiolite complexes, volcanic arcs, and deep-sea hydrothermal vents. It is also commonly found in kimberlite pipes, which are known for their diamond-bearing deposits. Serpentinite is typically found in areas of tectonic activity such as subduction zones and fault zones. It is also found in ophiolite complexes and in areas where ultramafic rocks have been altered by water.