Komatiite, Komati River, South Africa - Primordial Earth! NEW!
Great specimen. Fantastic spinifex textured bladed olivine is very evident!
Exceedingly rare specimen. Face polished.
Komatiite is a type of ultramafic mantle-derived volcanic rock. Komatiites have low silicon,
potassium and aluminum , and high to extremely high magnesium content. Komatiite was named
for its type locality along the Komati River, in South Africa.
True komatiites are very rare. The age restriction (3.8 to 2.8 Ga) is thought to be due to cooling of the mantle, which scientists think may have been up to 500 degrees C hotter during the early to middle Archaean. The early Earth had much higher heat production, due to the residual heat from planetary accretion, as well as the greater abundance of radioactive elements.
Geographically, komatiites are restricted in distribution to the Archaean shield areas. Komatiites occur with other ultramafic and high magneian mafic volcanic rocks in Archaean greenstone belts.
Pristine volcanic mineralogy of komatiites is composed of forstertic olivine, calcic and often chromian pyroxene, anorthite and chromite. Some of the highest magnesian komatiites with clear textural preservation are those of the Weltevreden Formation of the Barberton belt in South Africa (as this specimen is). The spinifex textured bladed olivine is very evident. (The "spinifex" texture is named after an Australian grass that grows in clumps with similar shapes).
Komatiites are associated with nickel and gold deposits in Australia, Canada, South Africa and most recently in the Guinana shield of South America.
Size: 45mm L X 39W X 22 mm D, Weight: 60.8 grams
Ships with certificate of authenticity, display case and information about the geological importance of the specimen. Legally collected.