Ultramafic rock but there are ultrapotassic and highly silica-under-saturated rocks with >18% MgO which can be considered "ultramafic". Ultrapotassic, ultramafic igneous rocks such as lamprophyre, lamproite and kimberlite are known to have reached the surface of the Earth. Although no modern eruptions have been observed, analogues are preserved. Most of these rocks occur as dikes, diatremes, lopoliths or laccoliths, and very rarely, intrusions. Most kimberlite and lamproite occurrences occur as volcanic and subvolcanic diatremes and maars; lavas are virtually unknown. Vents of Proterozoic lamproite (Argyle diamond mine), and Cenozoic lamproite (Gaussberg, Antarctica) are known, as are vents of Devonian lamprophyre (Scotland). Kimberlite
Kimberlite tailings performance of fixed-bed kimberlite tailings was studied and the adsorption capacity was found to be 0.27 mg/g of adsorbent. Film diffusion was found to be the rate-limiting factor for the removal of arsenic by kimberlite tailings. Adsorption of arsenic was found to be pH dependent and higher removal efficiencies were observed near neutral pH range. The arsenic uptake increased with increase in adsorbent dose. Spent kimberlite tailings could be regenerated with dilute NaOH. The proposed treatment methodology was applied to the groundwater samples collected from various places of North 24-Parganas district situated in West Bengal, India. The samples were analyzed