Pyrope garnets, sometimes known as chrome pyrope garnets or "anthill" garnets, have the most intense hues in the garnet world. They are called "chrome" because the coloring agent is chromium, the same element that gives ruby its intense color.

The name "anthill" garnet refers to the chrome pyropes found in the U.S. in AZ, NM and UT primarily, where Native Americans located deposits by inspecting anthills to see if any garnets had been brought to the surface as the ants tunnel, moving the small garnets out of the way and up to the surface. Garnets from this region are typically around 0.7 to 1.2ct. The ants simply move around and bypass any larger ones.

Ant hill garnets occur in a remote section of the Navajo Nation in Arizona. The gems have never been mined commercially because there aren't enough of them.

Offered in groups of 2, each 0.8 to 1.1ct at $24.00 for the group.

The first volcanic pipe found in the Lac de Gras region was the Point Lake kimberlite. The finders, two geologists, had found kimberlite indicator minerals in the area as early as 1985. Its discovery precipitated one of largest staking rushes in recent mining history, covering most of the area between Yellowknife and the Arctic coast. The Point Lake kimberlite pipe is one of 156 pipes known to be in the Lac de Gras region.

Offered in polished slices
Polished slices, in a 2'x2' plastic case, $30.00

Retrograde Eclogite

Retrograde Eclogite

Retrograde Eclogite

Eclogites form at mantle depths by burial metamorphism of oceanic crustal rocks. They are high grade, garnet-omphacite metamorphic rocks. An uplift and decompression of eclogites back to the surface often results in retrograde metamorphism. This results in the formation of new minerals and sometimes, reaction rims around the garnets. The original green omphacite pyroxene is often altered into a dull grey/bluish glaucophane along with muscovite.

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

Rubidian Lepidolite

Rubidian Lepidolite

This is a porphyritic carbonatite dyke rock from the Kaiserstuhl, the largest volcanic center in the Rhine Graben. There's a lot of great mineralogy in this one. Phonolites and extrusive carbonatites are present along with Mn-rich olivine, pyrochlore, Nb-rich perovskite, baddelyite, and the rare minerals zirconolite and calzirtite as Nb-rich varities with REE!

Offered in polished slices
Polished slices, in a 2'x2' plastic case, $28.00

Man Craton kimberlite

Man Craton kimberlite

Man Craton kimberlite

The Man craton in West Africa is an Archaean craton formerly joined to the Guyana craton (South America) that was rifted apart in the Mesozoic. Kimberlites of the Man craton include three Jurassic-aged clusters in Guinea. Most of the Man craton kimberlites are mineralogically classified as phlogopite kimberlites.

Offered in polished slices, micromounts
Polished slices, in a 2'x2' plastic case, $28.00

Ophiolite gabbro, Iceland

Ophiolite gabbro, Iceland

Ophiolite gabbro, Iceland

Ophiolites are segments of ocean crust and mantle tectonically exposed on land by obduction (overthrust), usually when an ocean basin closes. An ophiolite sequence consists of variably altered oceanic rocks, including marine sediments, ocean crust, and a part of the mantle.

The name ophiolite means "snakestone" from "ophio"(snake) and "lithos" (stone) in Greek. The rock sequence is named for the brilliant green, snake-like serpentine minerals which form in altered ocean crust and mantle. Ophiolites are rare. .

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

.Ijolite, Magnet Cove, Arkansas

.Ijolite, Magnet Cove, Arkansas

Ijolite, Magnet Cove, Arkansas

Magnet Cove is a 100-million-year old igneous intrusion of some rare and unusual rock types including Ijolites- all derived from a melt that was originally a CO2-rich basaltic liquid in the earth's upper mantle.

The Ijolite's of Magnet Cove are intrusive rocks that formed through the cooling and solidification of this basaltic liquid. They may form with or without crystallization, either intrusively below the surface, or on the surface as extrusive rocks.

Ijolites are composed of nepheline and an alkali pyroxene, usually aegirine-augite and are the plutonic equivalent of the volcanic nephelinites. Accessory minerals include garnet, titanite, perovskite, apatite, and calcite.

Offered in polished slices
Polished slices, in a 2'x2' plastic case, $28.00

Kimberlite in thin section

.Kimberlite, macrocrystal

.Kimberlite, macrocrystal

The DeBeer's mines in Kimberley, South Africa have produced and astounding variety of diamonds and kimberlite rocks including these macrocrystal specimens. All of these kimberlites were diamond bearing.

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

Eclogite , Bergan Arcs, Norway

Eclogite, Bergen Arcs, Norway

The Bergen Arcs, Norway is a folded stack of Proterozoic and Lower Paleozoic rock units defining a large fold structure that is clearly visible from topographic maps, geologic maps and satellite images. The rocks, strongly influenced by Caledonian deformation and metamorphism, generally show a pronounced foliation or metamorphic layering.

The classic area for Bergen Arcs eclogites is the northern part of Holsnøy, Meland, an island N of Bergen. They are striking in appearance with green omphacite and red-brown garnet. .

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

Basalt, Hakone Volcano

Basalt, Hakone Volcano

The Hakone volcano is located 80 km SW of Tokyo. It is a massive stratovolcano truncated by 2 overlapping calderas, The calderas were formed as a result of 2 major explosive eruptions about 180,000 and 49,000 years ago. Dome growth after the caldera formation occurred progressively to the south. The latest magmatic eruption from Hakone was 2900 years ago produceding a pyroclastic flow and a lava dome in the explosion crater.

The basaltic rocks from the Hakone volcano are mixtures of basic andesite magma and fragments of gabbroic rock. Most of the minerals of phenocrystic size and glomeroporphyritic crystal aggregates in the basaltic rocks, are xenocrysts that were derived from a gabbroic body lying beneath the volcano.

Offered in polished slices
Polished slices, in a 2'x2' plastic case, $28.00

Udachnaya pipe kimberlite

Udachnaya pipe kimberlite

Udachnaya pipe kimberlite

The Udachnaya Pipe is the largest diamond deposit located in the Daldyn-Alakit kimberlite field in Sakha Republic, of Russia. It is an open pit mine. It is located just outside the Arctic circle. It is more than 600m deep and the third deepest open pit mine in the world.

This is a calcite-rich hypabyssal kimberlite with clasts of olivine, diopside and phlogopite.

Offered in polished slices, micromounts
Polished slices, in a 2'x2' plastic case, $38.00

Olivine in basalt

Olivine in basalt

Olivine in basalt

From the San Carlos Indian Reservation¸ Gila County¸ Arizona, these are olivine in basalt xenoliths, which are thought to be pieces of the upper mantle delivered to Earth's surface in the magmas of deep-source volcanoes. There is an abundance of gemmy olivine in each specimen. .

Offered in polished slices
Polished slices, in a 2'x2' plastic case, $28.00

Banded Iron Formation

Banded Iron Formation

Banded Iron Formation

Banded iron formations (BIF) are distinctive geological units of sedimentary rock that are almost always of Precambrian age. A typical BIF consists of repeated, thin layers (a few millimeters to a few centimeters in thickness) of silver to black iron oxides, either magnetite (Fe3O4) or hematite (Fe2O3), alternating with bands of iron-poor shales and cherts, often red in color, of similar thickness, and containing microbands (sub-millimeter) of iron oxides.

Some of the oldest known rock formations, formed over 3.7 billion years ago, include banded iron layers. Banded layers rich in iron were mostly deposited between 2.4 and 1.9 billion years ago. Banded iron formations are an important commercial source of iron ore such as the Pilbara region of Western Australia

Offered in polished slices
Polished slices, in a 2'x2' plastic case, $28.00

Jack Hills Zircon in thin section

Jack Hills Zircon in matrix

The Jack Hills are located in the Narryer Gneiss Terrane of the Yilgarn Craton, Western Australia. Detrital zircons with ages greater than 4 billion years old have been found in rocks from this Terrane.

This is the oldest dated material originating on Earth; the date is in the Cryptic era of the Hadean eon. They were found within a unit of the supracrustal sequence, a metamorphosed conglomerate considered to have an age ~3.0 Ga. Given the detrital nature of the rock unit, the zircons are sourced from pre-existing rocks which were then weathered and the resultant sediment deposited as sedimentary rock.

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

Chromite

Chromite occurs in basic and ultrabasic igneous rocks and in metamorphic and sedimentary rocks that are produced when chromite-bearing rocks are altered by heat or weathering.

It is an oxide mineral composed of chromium, iron and oxygen. It's dark gray to black in color with a metallic to submetallic luster and a high specific gravity similar to magnetite.

Chromite is important because it is the only economic ore of chromium, an essential element for a wide variety of metal, chemical and manufactured products. Trace amounts of chromium produce the color in many minerals and gemstones. The red color of ruby, the pink of some sapphires and the green color of emerald are caused by tiny amounts of chromium.

Offered in polished slices
Polished slices, in a 2'x2' plastic case, $28.00

Lamprophyre, West Greenland

Lamprophyre, West Greenland

West Greenland has been the site of some excellent mantle-related geology. Kimberlites, lamproites, and ultramafic lamprophyres have all been reported.

Ultramafic lamprophyres are rare, they mineralogically resemble kimberlites and their classification is highly ambiguous. Still however, lamprophyres are defined as a group of rocks which are strongly porphyritic in mafic minerals, typically biotite, amphiboles and pyroxenes, with any feldspar being confined to the groundmass.

Offered in polished slices,
Polished slices, in a 2'x2' plastic case, $28.00

Cratrer of Diamonds Mine Kimberlite

Cratrer of Diamonds Mine Kimberlite

Sometime around 100 million years ago a deep-source volcanic eruption occurred in what is now Arkansas. Rising magma, rich in gases, expanded thousands of times in volume from the tremendous pressures at mantle depth. The expanding gas, carrying xenoliths of mantle-rich geology, exploded at the Earth's surface covering the surrounding area. These xenoliths were fragments of mantle rock - kimberlites, lamproites, alnoites with some of the kimberlites containing diamonds.

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

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Eclogite,Lahtojoki kimberlite pipe, Finland

Eclogite, Lahtojoki kimberlite pipe, Finland

Eclogites constitute a minor portion of the mantle-derived xenoliths in the eastern Finland kimberlites. They have been derived from the depth interval of 150-230 km where they are inferred to occur as thin layers or small lenses of coarse-grained garnet peridotites. Their chemical and isotopic composition suggest that they represent Proterozoic mantle-derived melts or cumulates rather than subducted oceanic lithosphere.

Offered in polished slices
Polished slices, in a 2'x2' plastic case, $28.00