How to Identify Basalt

Gabbro has the same composition as basalt.
••• Hemera Technologies/ Images

Basalt, a volcanic igneous rock, occurs worldwide, but especially in India, Scotland, Greenland, Iceland, Canada and the northwestern United States. Most basalt occurs as lava flows, in narrow dykes or sills. It's the basalt from lava flows that make up the enormous sheets of a lava plateau. This rock is easy to identify.

    Note the rock's color. Basalt appears black or grayish-black, sometimes with a greenish or reddish crust.

    Feel its texture. Basalt consists of a fine and even-grain. The dense rock has no crystals or minerals discernible to the naked eye. When freshly broken, basalt has a dull surface.

    Determine its structure with your naked eye or a microscope. Often vesicular or amygdaloidal, basalt has columnar jointing.

    Examine your rock's composition with a microscope. Basalt occurs more often as pyroxene (shiny, black) and as plagioclase (tabular, white-gray). The presence of olivine gives basalt a green, glassy appearance and is called olivine basalt. Also present may be iron ore (ilmenite and/or magnetite) or bronze-colored biottie.


    • Varieties of basalt include olivine basalt and quartz basalt, which contains a minuscule amount of quartz. Basalt is used as a source of iron ore, roadstone aggregate, sapphires or native copper.

Related Articles

How to Tell the Difference Between Talc & Gypsum
Interesting Facts About Quartzite
How to Identify Sandstone
Differences Between Foliated & Non-Foliated Metamorphic...
How to Identify Rough Gem Stones
How to Recognize Rough Agate
Physical Properties of Calcite & Quartz
How to Identify Valuable Rocks
List of Rare Minerals
How to Identify Obsidian
What Are the Properties of Igneous Rocks?
List of the Minerals Found in the State of Washington
Where Is the Mineral Topaz Found?
How to Identify Unpolished Agates
What Minerals Make Up Pumice?
Important Uses of Sphalerite
How to Find Agates
How to Tell if a Rock Is a Meteorite?
Types of Intrusive Igneous Rock With Large Crystals
The Different Kinds of Missouri Stone Used for Flint...

Dont Go!

We Have More Great Sciencing Articles!