Kimberlite
Image: <a rel="nofollow" class="external text" href="https://www.flickr.com/people/47445767@N05">James St. John</a> (CC BY 2.0)
Mineral NameKimberlite
Chemical FormulaVariable (ultramafic rock, rich in Mg, Fe, K, and volatiles)
Streak Colorgrayish-brown to dark gray
Cleavagenot applicable (rock)
Fractureuneven to conchoidal
Specific Gravity2.5
Colorsdark gray, black, greenish-black
Transparencyopaque
Type LocalityGates-Adah Kimberlite Dike, Pennsylvania, USA
Mineral GroupIgneous rock (ultramafic, ultrapotassic)
Useshost rock for diamonds (gemstone and industrial), scientific research
Associated Mineralsolivine, phlogopite, pyroxene, garnet, ilmenite, chromite, diamond
Description
A dark gray to black, fine-grained igneous rock with a porphyritic texture, displaying scattered larger crystals (phenocrysts) and shiny metallic or vitreous inclusions within a duller matrix.
Geological Context
Kimberlites are volatile-rich, potassic, ultramafic igneous rocks that originate deep within the Earth's mantle and are emplaced rapidly to the surface through pipe-like structures, often bringing diamonds from great depths.
