The Lac de Gras kimberlite field is a group of Late Cretaceous to Eocene age diatremes in the Northwest Territories, Canada. Within this field are located two world class diamond mines called Ekati and Diavik. This diamondiferous kimberlite is from the Diavik open pit mine. In this specimen: lots of phenocrysts of olivine, pyrope garnet serpententinized in an olivine-rich matrix.

Offered in polished slices.
Polished slice, in a 2"x2" plastic case, $32.00

This is diamondiferous lamproite from the Akluilak dyke, a part of the Dubawnt ultrapotassic dike swarn west of Hudson Bay, Nunavut, Canada and is thought to be associated with the magmatic event responsible for the formation of the Proterozoic (1850 Ma) Christopher Island Formation volcanics.

Offered in polished slices.
Polished slice, in a 2"x2" plastic case, $32.00

Nepheline Syenite in thin section

.Groundmass photomicrograph, Nepheline Syenite

From the legendary mining locality of Minas Gerais, Brazil, at the Salitre I alkaline intrusion, this rock contains a rare mineral association on Earth - alkali feldspar coexisting with perovskite. Normally the silica content of feldspar-bearing rocks is too high for perovskite but the Sr and REE content of the rock is so high the stability field of perovskite is expanded. So, why so unusual and rare? Perovskite is commonly found associated with very anorthite-rich feldspar in anhydrous LUNAR basalts!

Offered in polished slices.
Polished slice, in a 2'x2' plastic case, $32.00

.Kimberlite, Chicken Park Pipe in thin section.

Groundmass photomicrograph, Kimberlite, Chicken Park Pipe.

Great name, great locality, colorful rock! Chicken Park kimberlite, near Red Feathers Lake, Northern Colorado, USA, has an emplacement age of 614.5 my. The kimberlite was initially found during coarse sampling with a backhoe at around a one meter depth. Colorful garnet in each kimberlite sample.

Offered in polished slices.
Polished slice, in a 2"x2" plastic case, $28.00

Balsam Gap Dunite in thin section.

Groundmass photomicrograph of Balsam Gap Dunite

The Balsam Gap, North Carolina, USA, dunite mineral assemblage is greater than 90% olivine, with minor amounts of other minerals such as pyroxene, chromite and pyrope. Dunite, the olivine-rich end-member of the peridotite group of mantle-derived rocks, is rarely found within continental rocks. Dunite from Balsam Gap is believed to have occurred at the base of an ophiolite sequence where slabs of mantle rock from a subduction zone were thrust onto continental crust by obduction during continental collisions.

Offered in polished slices.
Polished slice, in a 2"x2" plastic case, $28.00

Spinel Lherzolite in thin section.

Groundmass photomicrograph of Spinel Lherzolite

This is an extremely attractive, coarse-grained, superfresh (had enough adjectives?!?!) spinel lherzolite with abundant chrome diopside inclusions. It's a very nice Australian xenolith from Mt. Leura ( the name means "big nose" in local aboriginal dialect), Victoria, Australia.

Offered in polished slices.
Angular section in a 2"x2" plastic case, $32.00

Chromite-rich Dunite in thin section

Groundmass image of chromite-rich dunite

Kimberlite,ugandite in thin section

Kimberlite-ugandite groundmass.

Archean Karelian Craton kimberlite in thin section

Archean Karelian Craton kimberlite groundmass

Over twenty-four intrusive bodies, mostly kimberlitic diatremes, but also including hypabyssal kimberlites, olivine lamproites and ultramafic lamprophyres are being studied within the Archean Karelian Craton in Finland. Kimberlites from the Karelian Craton exhibit typical mineralogy of Group I kimberlites including abundant macrocrysts of olivine, picroilmenite, Cr-diopside, pyrope garnet; phenocrysts of olivine and microphenocrysts of monticellite, perovskite and spinel in a calcite + serpentine matrix.

Offered in polished slices.
Polished slice, in a 2"x2" plastic case, $33.00

Alkali Olivine Basalt in thin section

Alkali Olivine Basalt groundmass.

Deformed Harzburgite thin section.

Deformed Harzburgite groundmass

This is a great specimen, deformed harzburgite - from below the petrological Moho boundary!. It consists of ribbons of relatively soft orthopyroxene around rounded olivine grains.Ophiolite harzburgite is a variety of peridotite, which is thought to represent oceanic crust and the underlying oceanic mantle exposed during collision with continental crust.

Offered in polished slices.
Polished slice, in a 2"x2" plastic case, $38.00

Alnoite, Mount Moroto thin section

Alnoite, Mount Moroto groundmass

Alnoites (named after the island of Alno in Norway) are rare rocks. They are a subgroup of lamprophyres. Alnoites contain olivine, augite, brown biotite and melilite, are free from felspar, and contain very low percentages of silica. They are essentially "dike rocks," occurring as dikes and thin sills, and are also found as marginal facies of plutonic intrusions. Alnoites have a close association with nepheline or leucite syenites and similar rocks rich in alkalies.

Offered in polished slices.
Polished slice, in a 2"x2" plastic case, $32.00

Cumberlandite in thin section

Cumberlandite groundmass

Cumberlandite is not kimberlitic but it is a rare mixing of mineralogy from an extinct volcano that presents itself in only one place on Earth. It's an ultrabasic igneous rock, transitional to peridotite, from Cumberland, Rhode Island. The rock is greenish black and shows large, white plagioclase crystals in a black granular groundmass. A hand lens shows some labradorite, olivine, magnetite, ilmenite, and accessory spinel. The olivine forms nearly half the rock and is set in a matrix of the other minerals, 40 percent or more of the rock being ilmenite and magnetite. The whitish-gray patches are single large crystals of plagioclase feldspar. The black component is the finely-crystalline groundmass, consisting of magnetite, ilmenite, and olivine (partially serpentinized by orogenic events).

Offered in polished slices.
Polished slice, in a 2"x2" plastic case, $28.00

Bergen Arcs eclogite thin section.

Bergen Arcs eclogite groundmass

The Bergen Arcs in Norway are famous for rare and rather beautiful rocks known as eclogites. Striking, coarse-grained, and characterized by large pink garnets and a greenish matrix rich in pyroxene.

Offered in polished slices.
Polished slice, in a 2"x2" plastic case, $38.00

Moses Rock dike kimberlite thin section

Moses Rock dike kimberlite groundmass

The Moses Rock dike lies in the eastern part of Monument Valley, about 5 miles southeast of Mexican Hat, Utah, near the center of the Colorado Plateau Province, where sedimentary rocks of Paleozoica and Mesozoica age are exposed. Kimberlite was emplaced as large, discrete, angular rocks within the dike.

Offered in polished slices.
Polished slice, in a 2"x2" plastic case, $32.00

Olivine phlogopite lamproite thin section

Olivine phlogopite lamproite groundmass

This is a complex rock, full of xenocrysts and xenoliths, large olivine xenoliths of mantle origin, a matrix rich in phlogopite and containing perovskite, and finally, if all the above is not enough harzburgitic xenocrysts!

Offered in polished slices.
Polished slice, in a 2"x2" plastic case, $28.00

Mirny Mine kimberlite thin section

Mirny Mine kimberlite.

Mirny Mine is an open pit diamond mine located in Mirny, Eastern Siberia, Russia. The mine is 525 meters (1,720 ft) deep and has a diameter of 1,200 m and is the second largest excavated hole in the world, after Bingham Canyon Mine. The airspace above the mine is closed for helicopters because of a few incidents in which they were sucked in by the downward air flow. Kimberlite indicator minerals include red garnet, chromium diopside, and yellow-green olivine throughout the groundmass. A very hard locality to acquire.

Offered in polished slices.
Polished slice, in a 2"x2" plastic case, $32.00

Harzburgite, Mantle Xenolith thin section

Harzburgite, Mantle Xenolith groundmass.

This Harzburgite is one of the most attractive specimens of mantle rock. It's an ultramafic igneous rock and a variety of peridotite. Its matrix is studded with green inclusions of chromium diopside. The locality is from the Kaapval Craton, in Kimberley, South Africa.

Offered in polished slices.
Polished slice, in a 2"x2" plastic case, $33.00

Alkali olivine basalt in thin section

Alkali olivine basalt groundmass.