Igneous

Kimberlite

Kimberlite (Porphyritic Peridotite)

Hardness: 6-7 (primarily due to olivine and pyroxene); Color: Greenish-grey, blue-grey, or brownish-yellow; Luster: Greasy to vitreous; Crystal structure: Porphyritic (large crystals in a fine-grained matrix); Specific gravity: 2.7–3.3; Contains xenocrysts like pyrope garnet, phlogopite, and chrome diopside.

Hardness: 6-7 (primarily due to olivine and pyroxene)
Color: Greenish-grey, blue-grey, or brownish-yellow
Luster: Greasy to vitreous

Identified March 14, 2026More igneous →

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Physical properties

Formation & geological history

Formed through high-pressure volcanic eruptions originating in the Earth's mantle (150–450 km deep). These 'kimberlite pipes' were rapidly emplaced through the crust during various intervals, largely between 70 to 1,200 million years ago.

Uses & applications

Primary source of industrial and gem-quality diamonds; also collected as a rare mantle geological specimen and used for scientific research into the Earth's deep interior.

Geological facts

Kimberlite is named after the town of Kimberley in South Africa, where a 83.5-carat diamond called the 'Star of South Africa' was discovered in 1869, starting a major diamond rush.

Field identification & locations

Identify in the field by looking for 'blue ground' (unweathered) or 'yellow ground' (oxidized) pipes containing rounded olivine crystals and bright red garnets. Common locations include South Africa, Russia (Siberia), Canada (NWT), and parts of the United States (Arkansas and Wyoming).

Other igneous specimens

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous