Kimberlite and lamproite rocks contain diamonds.
In this article, we shall discuss the formation, characteristics, and chemical components of kimberlite and lamproite rocks—also, places where the rocks containing diamonds can be found.
2 Rocks That Contain Diamonds
1. Kimberlite Rocks
The rocks are a type of igneous rock that forms when magma flows out of deep earth fractures.
Magma existing in Kimberlite pipes pushes diamonds and other stones rapidly (a few hours) through the earth’s crust and mantle.
The rapid and violent eruption of kimberlite releases carbon dioxide and other volatile components.
The rocks are found deep inside the mantle, within 150km to 450km.
Through intense pressure, the formation of diamonds occurs.
The depths are more significant than other types of igneous rocks.
Diamonds inside the rock are crystallized carbon chain atoms.
The dense concentration of the rocks’ carbon chains makes the stones unique.
The Kimberlite texture ranges consist of a porphyritic texture with rounded crystals (phenocrysts) and surrounded by groundmass (grained matrix).
The rocks are rich in
- Mica minerals
- Carbonate minerals
- Magnesium ilmenite
These gems are in significantly higher quantities than diamonds in the rock.
Extractors use the components for prospecting diamond in a kimberlite.
Extraction of the stone involves sheen shovels and massive tracks.
Kimberlite magmas are low in silica and high in incompatible trace elements like potassium and magnesium.
The key features of the rocks include:
Cloudy rocks characterize the unmined diamond. When mined, diamonds are well rounded and smooth.
Classes of Kimberlite
The rocks entail three classes based on studies done on large kimberlite deposits.
Crater Facies Kimberlite
The features of unweathered kimberlite on surface morphology are craters with up to 2 km diameter and several hundred floors below the ground level.
The crater deepens in the middle and is rounded by a tuff ring less than 30m than its diameter.
The crater category includes pyroclastic and epiclastic rocks.
Diatreme Facies Kimberlite
The kimberlite diameter ranges between 1 to 2 km deep with carrot-shaped bodies (circular to elliptical) at the surface.
The rocks have dip contacts of 80 to 85 degrees.
Fragmented volcanoclastic material and xenoliths characterize the class.
Hypabyssal Facies Kimberlite
The rocks are due to the crystallization of volatile and hot magma.
Typically, the stones lack fragmentation properties and appear igneous.
Textural features include; globular segregations in a carbonate-rich matrix, calcite-serpentine segregations matrix, and pseudoporphyritic texture.
Places Where We Can Find Kimberlite Rocks
Piped structures that carry rough circular vertical edges cross-sections contain kimberlite rocks.
Kimberlite pipes and igneous dykes are vertical-edged structures.
These rocks can be found in mines in countries such as Botswana, South Africa, Russia, Angola, Australia, and Canada.
Lamproites are ultrapotassic mantles derived from subvolcanic and volcanic rocks.
Though the stones are widespread geographically, they’re insignificant in volume.
The breccia tuff erodes quickly, leading to diamonds.
The formation occurs at depths greater than 150kms.
Thrusting molten materials into the surface through volcanic pipes results in lamproite materials.
The materials carry along with diamonds and xenoliths from eclogite mantle areas where stabilization of diamond occurs.
The rocks are volcanically varied.
The diameter styles, cone edifices, and cinder cones are known.
The rocks are brittle black or dark brown with white or yellow spots of weathered olivine. Other features include:
The rocks are in dyke pipes which are rich in magnesium and potassium but poor in silicon.
The abundant venting pyroclastics is due to magmas weakly consolidated into sedimentary sequences.
Lamproite contains the following main components;
- Leucite Richterite
Other secondary features include:
The quantity of chemical components in lamproite depends on the depth of origin, melting point degree, and composition of melted rocks which produce them.
The texture of lamproite ranges from vesicular to dense, massive to fragmental, porphyritic, and aphanitic.
Places Where We Can Find Lamproite Rocks
Terrains in Western Australia and the Mesozoic and Palaeozoic regions in Southern Spain are places where we can find lamproite rocks.
The ages of the rocks vary widely, with some as old as over 5,000 years.
Kimberlite and lamproite rocks require high temperatures to form — rapid volcanic eruption results in diamond-containing stones.
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