Lamproite is a peralkaline volcanic rock. Olivine lamproite pyroclastic rocks and dikes are often hosts for diamonds. The diamonds occur as xenocrysts that have been carried to the surface or to shallow depths by the lamproite diapiric intrusions. Volcanic rock on North America Plutonic rock on North America Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... Olivine The mineral olivine is a magnesium iron silicate with the formula (Mg,Fe)2SiO4 in which the ratio of magnesium and iron varies between the two endmembers of the series: forsterite (Mg-rich) and fayalite (Fe-rich). ... Pyroclastic rocks are formed from lavas which are ejected into the air, as occur in pyroclastic flows or Plinian eruptions. ... A dike in geology refers to a tabular intrusive igneous body. ... A scattering of round-brilliant cut diamonds shows off the many reflecting facets. ... Pluton redirects here. ... Pluton redirects here. ...

Lamproites occupy relatively shallow bowl shaped craters up to 1.5 km in diameter and about 300 m in depth.

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. Forsterite (Mg2SiO4) is the magnesium rich end-member of the olivine solid-solution series. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metal Group, Period, Block 8 (VIIIB), 4, d Density, Hardness 7874 kg/m3, 4. ... Leucite or amphigene is a rock-forming mineral composed of potassium and aluminium metasilicate KAl(SiO3)2. ... General Name, Symbol, Number Titanium, Ti, 22 Chemical series transition metals Group, Period, Block 4, 4, d Density, Hardness 4507 kg/m3, 6 Appearance Silvery metallic Atomic properties Atomic weight 47. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13 (IIIA), 3, p Density, Hardness 2700 kg/m3, 2. ... Phlogopite is a yellow, greenish or reddish brown member of the mica family. ... General Name, Symbol, Number potassium, K, 19 Series alkali metals Group, Period, Block 1(IA), 4, s Density, Hardness 856 kg/m3, 0. ... Diopside is a monoclinic pyroxene mineral with composition MgCaSi2O6. ... Potassium oxide or potash (formula K2O) is a compound of potassium and oxygen used mainly as a fertilizer. ... General Name, Symbol, Number chromium, Cr, 24 Chemical series transition metals Group, Period, Block 6 (VIB), 4, d Appearance silvery metallic Atomic properties Atomic weight 51. ... General Name, Symbol, Number nickel, Ni, 28 Chemical series transition metals Group, Period, Block 10 , 4, d Density, Hardness 8908 kg/m³, 4. ... Talc block Talc is a mineral composed of hydrated magnesium silicate with the chemical formula H2Mg3(SiO3)4 or Mg3Si4O10(OH)2. ... Carbonate is an anion with a charge of -2 and an empirical formula of CO32-. An aqueous solution of carbon dioxide contains a minute amount of H2CO3, called carbonic acid, which dissociates to form hydrogen ions and carbonate ions. ... Serpentine Serpentine is a group of common rock-forming hydrous magnesium iron phyllosilicate ((Mg,Fe)3Si2O5(OH)4) minerals. ... The term Chlorite can refer to the following meanings: The chlorite group of clay minerals. ... Magnetite is a magnetic mineral form of both iron(II) oxide and iron(III) oxide or (iron(II,III) oxide), with chemical formula , one of several iron oxides and a member of the spinel group. ... Zeolite Zeolites (Greek, zein,to boil;lithos,a stone) are minerals that have a porous structure. ... Quartz is the second most abundant mineral in the Earths crust. ...

Lamproites form from partially melted mantle at depths exceeding 150 km. The molten material is forced to the surface in volcanic pipes, bringing with it xenoliths and diamonds from the harzburgitic peridotite or eclogite mantle regions where diamond formation is stabilized. Earth cutaway from core to exosphere. ... Volcanic pipes are subterranean geological structures formed by the violent, supersonic eruption of deep-origin volcanoes. ... A xenolith (Greek: foreign rock) is a rock which becomes enveloped in a larger rock during the latters development and hardening. ... Peridotite Peridotite is a dense, coarse grained ultrabasic rock, consisting mainly of the minerals olivine and pyroxene. ... Eclogite is a coarse-grained, mafic-to-ultramafic grouping of metamorphic rocks of special interest on account of the variety of minerals they contain and their microscopic structures and geological relationships. ...

The economic significance of lamproite became known with the 1979 discovery of the Argyle diamond pipe in Western Australia. This discovery led to the intense study and re-evaluation of other known lamproite occurrences worldwide; previously only kimberlite pipes were considered economically viable sources of diamonds. 1979 is a common year starting on Monday. ... The Argyle diamond mine is a diamond mine located in Australia. ... Motto: Cygnis Insignis (Distinguished by its swans) Nickname: Wildflower State Other Australian states and territories Capital Perth Government Governor Premier Const. ... Hewn kimberlite core sample from the James Bay Lowlands region of Northern Ontario, Canada. ...

The diamonds of Crater of Diamonds State Park near Murfreesboro, Arkansas are found in a lamproite host. The Crater of Diamonds is an Arkansas State Park located in Murfreesboro in Pike County, Arkansas containing the only diamond mine open to the public in North America. ... Murfreesboro is a city located in Pike County, Arkansas. ...

References

• LAMPROITE-HOSTED DIAMONDS (http://www.em.gov.bc.ca/Mining/Geolsurv/MetallicMinerals/MineralDepositProfiles/profiles/n03.htm) retrieved June 7, 2005
• Microscopic image of lamproite (http://www.microscopy.fsu.edu/primer/techniques/polarized/gallery/pages/lamproitesmall.html) retrieved June 7, 2005
• Argyle pipe (http://volcano.und.nodak.edu/vwdocs/volc_images/australia/argyle/argyle.html) retrieved June 7, 2005