Diabase is a dark-colored fine-grained, intrusive igneous rock. Diabase is also known as dolerite in the United Kingdom and a few other countries.

Rock Composition

Its mineral composition is similar to basalt and gabbro. The grain size is the main difference between basalt, gabbro, and diabase. It is determined by the cooling rates.

Diabase comprises 40-70% plagioclase feldspar (known as labradorite). The remainder is made of pyroxene minerals such as augite. Hornblende, olivine, magnetite, and quartz are also found in diabase rocks.

The mineral species found in diabase mostly have perfect cleavage due to tiny interlocking grains. It doesn’t impact the rock’s durability concern while using the rock as a construction material.

Diabase Rock Formation

Diabase formation has two requirements;

1. A basaltic magma source
2. Shallow emplacement (the process or state of setting something in place or being set in place) and cooling in a small subsurface structure such as a dike, sill, laccolith, and lopolith

Where is Diabase Found?

Diabase is generally found in smaller, shallow intrusive bodies like dikes and sills. Its dikes occur in crustal extension regions. It is often found in dike swarms or sills from a single volcanic center. Diabase is found in the following places.

• Palisades Sill on the Hudson River
• Dike complexes in Skye, Rum, Mull, and Arran of western Scotland
• Slieve Gullion region of Ireland
• Dike swarms in northern England
• Parts of the Deccan traps in India
• Abundantly found in Curaçao, an island off the coast of Venezuela
• Chad in central Africa
• Devonian age diabase in Thuringian-Franconian-Vogtland Slate Mountains of central Germany

Diabase Uses

Diabase has been used for centuries for famous architectural structures. It is used in the crushed form and as a dimension stone.

1. Crushed Stone: Its main use is in the construction industry. The common applications include:

• Highway construction
• Concrete slab construction
• Aggregate in concrete and asphalt paving material
• Drainage stone in foundations
• Filter stone in sewage disposal drain fields
• Railroad construction
• Landscaping

2. Dimension Stone: Diabase in block-shaped pieces is used to build foundations, walls, support, and masonry. It is also used as an architectural, paving, and monument stone.

Interesting facts about diabase and its commercial use

• Diabase from some extraction mines contains abundant crystals of labradorite that produce colorful reflections (labradorescence). Polished diabase is an attractive construction stone.
• The minerals (pyroxene & feldspars) in unpolished and untreated diabase form a weathering rind when exposed to elements like air and water. The black stone can alter to chalky white, tan, or gray color.

The famous structures build using Diabase

 Vorontsov Palace, Crimea; built in 1800s has exterior made from diabase

Stonehenge, Salisbury Plain in Wiltshire, England, is made from diabase pillars that came from Carn Meini Quarry in the Preseli Mountains of southwestern Wales.

Marine Corps War Memorial, near Arlington, Virginia, unveiled on November 10, 1954 is made of black diabase.