Where is pegmatite found

Pegmatites usually do not support large mining operations that employ dozens of workers and have continuous activity of many years. Crabtree pegmatite: One of the most interesting pegmatites is the Crabtree Pegmatite of western North Carolina. It is a granitic pegmatite that intrudes the boundary between two rock units in a dike that is up to two meters wide.

It was mined for emeralds by a series of owners, which included Tiffany and Company, between and the s. Many fine clear emeralds were produced, and much of the rock was sold as "emerald matrix" for slabbing and cabochon cutting.

This specimen is about 7 x 7 x 7 centimeters in size and contains numerous small emerald crystals that are several millimeters in length. In the early stages of crystallization, the ions that form high-temperature minerals are depleted from the melt.

Rare ions that do not participate in the crystallization of common rock-forming minerals become concentrated in the melt and in the excluded water. These ions can form the rare minerals that are often found in pegmatites.

Examples are small ions such as lithium and beryllium that form spodumene and beryl; or large ions such as tantalum and niobium that form minerals such as tantalite and niobite. Rare elements concentrated in large crystals make pegmatite a potential source of valuable ore. Polished pegmatite countertop: A portion of a countertop made from polished pegmatite. Large crystals of feldspar, smoky quartz, and hornblende are visible. The view seen here is about 12 inches across.

Pegmatite rock has very few uses. However, pegmatite deposits often contain gemstones , industrial minerals, and rare minerals. Pegmatite rock has limited use as an architectural stone.

Occasionally it is encountered in a dimension stone quarry that produces granite for architectural use. If the pegmatite is sound and attractive, it might be cut into slabs and polished for building facing, countertops, tile or other decorative stone products and sold commercially as a "granite. Large crystals of feldspar, quartz, and hornblende are visible.

The view seen here is about six inches across. Gemstones found in pegmatite include: amazonite, apatite , aquamarine , beryl , chrysoberyl , emerald , garnet , goshenite , heliodor , kunzite , lepidolite , morganite , spodumene , topaz , tourmaline , zircon , and many others. Large crystals of excellent-quality material are often found in pegmatite. Pegmatite is the host rock for many rare mineral deposits.

These minerals can be commercial sources of: beryllium , bismuth, boron, cesium, lithium, molybdenum, niobium, tantalum, tin, titanium, tungsten, and many other elements. In most cases the mining operations are very small, employing less than a dozen people.

If the mine contains nice crystals, the minerals are often more valuable as mineral specimens and faceting rough than being sold as an ore.

The best way to learn about rocks is to have specimens available for testing and examination. In nature, pegmatite fields do not show such a zoning. In Leinster, Ireland Figure C , spodumene- and barren pegmatites are aligned in a shear zone.

GREENPEG develops new genetic models, which imply that rare metal enrichments and distribution of most European pegmatites are controlled by the chemistry and degree of partial melting of wall rocks and the presence of tectonic structures.

Pegmatites Many of the raw materials for green energy production can be sourced from a rock type known as pegmatite. Pegmatites as a Cultural Heritage Discover the mineral wealth and economic meaning of pegmatite mining or just the beauty of their exposure in the landscape such as in Pleystein. Towards a better understanding of Pegmatites Pegmatites, illustrated as colored dots in Figures A to C, occur in fields.

Gemstones are also associated such as topaz, tourmaline and aquamarine. Large crystal growth in pegmatites are not attributed to slow rate of crystallisation but indeed the low-viscosity fluids are the reason.

In the early stages of magma crystallisation, the melt contains the water dissolved with other volatile like chlorine, fluorine and carbon dioxide. The water in the early crystallisation is remained in the melt as crystal start to form, water then separates and escapes the melt. The pockets of water are super heated that contains huge amount of dissolved ions.

This water moves freely and are more mobile than that of the melt which when crystallises produce large crystal which are the pegmatites. The mineralogy of a pegmatite is in most cases dominated by some form of feldspar, often with mica and usually with quartz, being altogether "granitic" in character. Beyond that, pegmatite may include most minerals associated with granite and granite-associated hydrothermal systems, granite-associated mineralisation styles, for example greisens, and somewhat with skarn associated mineralisation.

It is however impossible to quantify the mineralogy of pegmatite in simple terms because of their varied mineralogy and difficulty in estimating the modal abundance of mineral species which are of only a trace amount.

This is because of the difficulty in counting and sampling mineral grains in a rock which may have crystals from centimetres to meters across. Garnet, commonly almandine or spessartine, is a common mineral within pegmatites intruding mafic and carbonate-bearing sequences. Pegmatites associated with granitic domes within the Archaean Yilgarn Craton intruding ultramafic and mafic rocks contain red, orange and brown almandine garnet. Tantalum and niobium minerals columbite, tantalite, niobite are found in association with spodumene, lepidolite, tourmaline, cassiterite in the massive Greenbushes Pegmatite in the Yilgarn Craton of Western Australia, considered a typical metamorphic pegmatite unassociated with granite.

Pegmatite sample representative is difficult due to the large size of the constituent mineral crystals. Often, bulk samples of some kg of rock must be crushed to obtain a meaningful and repeatable result.