Gabbro

Image: <a href="//commons.wikimedia.org/wiki/User:Wilson44691" title="User:Wilson44691">Wilson44691</a> (<bdi lang="en" dir="ltr" title="archived on 7 September 2008 at the Wayback Machine"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20080907220913/http://www.wooster.edu/geology/mwilson.html">Mark A. Wilson</a> at the <span lang="en" dir="ltr"><a href="https://en.wikipedia.org/wiki/Wayback_Machine" class="extiw" title="en:Wayback Machine"><span lang="en" dir="ltr">Wayback Machine</span></a></span></bdi>, Department of Geology, The College of Wooster). (Public domain)

Mineral NameGabbro

Chemical FormulaComplex silicate (rock composed primarily of plagioclase and pyroxene)

Mohs Hardness6

Streak ColorGray to greenish-gray

CleavageNot applicable (rock); constituent minerals exhibit cleavage (e.g., plagioclase: 2 directions at ~90°, pyroxene: 2 directions at ~90°)

FractureUneven to subconchoidal

Specific Gravity2.8

Colorsdark gray, black, greenish-black

TransparencyOpaque

Type LocalityRock Creek Canyon, eastern Sierra Nevada, California

Mineral GroupIgneous rock (mafic, intrusive)

Usesconstruction aggregate, dimension stone, countertops, road material

Associated Mineralsplagioclase feldspar, pyroxene, olivine, amphibole, magnetite, ilmenite

Raritycommon

Description

A dark gray to black, coarse-grained igneous rock specimen with visible interlocking crystals, exhibiting a somewhat rough, uneven surface and a few brighter, reflective mineral grains.

Geological Context

Gabbro is a mafic intrusive igneous rock that forms from the slow crystallization of magnesium- and iron-rich magma deep beneath the Earth's surface. It is the intrusive equivalent of basalt and is a major component of the lower oceanic crust.

Explore Tools Browse All Specimens

Related Specimens

Jade (Nephrite)

Pterosaur Fossil

Tremolite

Chlorite

Heliodor

Magnetite