Lamproites are geographically widespread yet are volumetrically insignificant. Unlike kimberlites which are found exclusively in Archaean cratons, lamproites are found in crust of varying age, ranging from Archaean examples in Western Australia, to Palaeozoic in southern Spain. They are also widely varied in age, from Proterozoic to Holocene, the youngest known example being 56,000 +/- 5,000 years old.
Recent research and lead-lead isotope geochemistry has revealed that the source of lamproites may be transition zone melts of subducted lithosphere which has become trapped at the base of the lithospheric mantle. This observation also reconciles the depth of melting with the peculiar geochemistry, which is most easily explained by melting of already felsic material under deep mantle conditions.
Minerals typical of lamproites include: forsteritic olivine; high iron leucite; titanium-rich aluminium-poor phlogopite; potassium- and titanium-rich richterite; low aluminium diopside; and iron-rich sanidine. A variety of rare trace minerals occur. The rocks are high in potassium with 6 to 8% potassium oxide. High chromium and nickel content is typical. The rocks commonly are altered to talc with carbonate or serpentine, chlorite, and magnetite. Zeolites and quartz may also occur.
Lamproites are characterized by the presence of widely varying amounts (5-90 vol.%) of the following primary phases (Mitchell & Bergman, 1991):
The presence of all the above phases is not required in order to classify a rock as a lamproite. Any one mineral may be dominant, and this, together with the two or three other major minerals present, suffices to determine the petrographic name. The presence of the following minerals precludes a rock from being classified as a lamproite: primary plagioclase, melilite, monticellite, kalsilite, nepheline, Na-rich alkali feldspar, sodalite, nosean, hauyne, melanite, schorlomite or kimzeyite.
The Argyle diamond mine remains the only economically viable source of lamproite diamonds. This deposit differs markedly by having a high content of diamonds but low quality of most of stones. Research at Argyle diamond have shown that most of stones are of E-type, they originate from eclogite source rocks and were formed under high temperature ~1400 °C. The Argyle diamond mine is the main source of rare pink diamonds.
Olivine lamproite pyroclastic rocks and dikes are sometimes hosts for diamonds. The diamonds occur as xenocrysts that have been carried to the surface or to shallow depths by the lamproite diapiric intrusions.
Wyomingite diopside-leucite-phlogopite lamproite
Orendite diopside-sanidine-phiogopite lamproite
Madupite diopside madupitic lamproite
Cedricite diopside-leucite lamproite
Mamilite leucite-richterite lamproite
Wolgidite diopside-leucite-richterite madupitic lamproite
Fitzroyite leucite-phlogopite lamproite
Verite hyalo-olivine-diopside-phlogopite lamproit
Jumillite olivine-diopside-richterite madupitic lamproite
Fortunite hyalo-enstatite-phlogopite lamproite
Cancalite enstatite-sanidine-phlogopite lamproite