Geology Forum for Geologists

Diabase or dolerite is a type of igneous rock that is composed primarily of plagioclase feldspar, pyroxene, and sometimes olivine. Plagioclase feldspar, which is a type of feldspar that contains calcium and sodium, is typically the most abundant mineral in diabase.

In some cases, diabase can display white lines or streaks that are composed of plagioclase feldspar. These white lines are commonly referred to as feldspar laths or feldspar porphyroblasts, and they are often visible to the naked eye.

The formation of these white lines is typically the result of a process known as crystal growth or crystallization. When diabase cools and solidifies from a molten state, the plagioclase feldspar crystals grow at different rates, with some crystals growing faster than others. This can lead to the development of large, well-formed feldspar crystals that are visible as white lines within the rock.

The presence of feldspar laths or porphyroblasts in diabase can be useful for geologists in identifying and classifying the rock. It can also provide insights into the conditions under which the rock formed, such as the rate of cooling and the presence of other minerals or substances in the magma

Dolerite is a dark, igneous rock with a medium-grained texture that is composed primarily of plagioclase feldspar, pyroxene, and sometimes olivine. Some of the key features of dolerite are:

Color: Dolerite is typically dark-colored, ranging from black to dark gray.

Texture: It has a medium-grained texture, which means that the individual mineral grains are visible to the naked eye.

Hardness: Dolerite is a hard rock, with a Mohs hardness of around 6-7.

Density: Dolerite has a relatively high density, typically ranging from 2.8 to 3.0 g/cm3.

Composition: Dolerite is primarily composed of plagioclase feldspar, pyroxene, and sometimes olivine. It may also contain other minerals such as quartz, biotite, or hornblende.

Occurrence: Dolerite is a common rock type found in many parts of the world, including parts of Africa, Australia, Europe, and North America. It is often found in dykes and sills, and may also form large intrusive bodies known as plutons.

Uses: Dolerite is a popular building stone and is often used as an aggregate in road construction. It is also used in the construction of monuments, as a decorative stone, and as a source of crushed rock for various industrial processes.

The crystal system of dolerite is generally considered to be the holocrystalline equivalent of basalt, which means that it typically has a fine-grained or microcrystalline texture that does not allow for the identification of crystal faces. Therefore, it does not have a clearly defined crystal system. However, the individual mineral crystals that make up dolerite (such as plagioclase feldspar and pyroxene) have well-defined crystal systems, which are typically triclinic for plagioclase and monoclinic or orthorhombic for pyroxene.