Mineral of the Month

Mineral: Pyrite

Chemical Formula: FeS₂

Description: Gold in colour, with the crystals formed as solid cubes.

Formation: Forms when bacteria remove oxygen from sulphate in water, producing sulphide that reacts with iron. It is common in igneous rocks.

Uses: Used in ink, supplements, for water treatment, and as a source of sulphur.

Where can I see it?: Associated with sedimentary, igneous & metamorphic rocks, and commonly found in the replacement of fossils (pyritization), for example in molluscs at the Jurassic coast.

Fun Fact: Pyrite is also known as fool’s gold, as it has often been mistaken for gold.

Mineral: Quartz

Chemical Formula: SiO₂

Description: Usually clear with irregular surfaces, sometimes with sharp points. Quartz can come in many colours including Scottish Cairngorm smoky quartz.

Formation: Forms in igneous rocks via crystallisation, in metamorphic rocks, and as clasts in sedimentary rocks.

Uses: Used for jewellery, clocks, watches, computers, radios and more!

Where can I see it?: Found in igneous, metamorphic, and sedimentary rocks, it’s one of the most common minerals. Quartz can be seen on almost all UK beaches.

Fun Fact: Quartz can present as fine crystals in rocks, to very large crystals. For example, in Arkansas a crystal was found weighing 8000lbs, over 6ft tall.

Mineral: Apatite

Chemical Formula: Ca₅(PO₄)₃(Cl, F, OH)

Description: Hexagonal shaped crystals that can be translucent & coloured pale shades of greens, blues, yellows, or browns depending on formation conditions and chemical compositions.

Formation: Apatite can form in igneous, sedimentary or metamorphic rocks.

Uses: Used in fertiliser, ceramics, jewellery, and in dentistry.

Where can I see it?: Found in a range of geological settings all over the UK.

Fun Fact: It also forms as a component of teeth, bones, and fish scales; providing strength to structures.

Mineral: Amethyst (a type of quartz)

Chemical Formula: SiO₂

Description: Glassy, purple crystals that are hexagonal and pointy.

Formation: Amethyst forms when trace impurities of iron and other transition metals replace silicon atoms in the crystal structure of quartz. Exposure to light causes the purple colour to fade. It commonly forms in voids of igneous rocks.

Uses: For jewellery, decoration, & has spiritual uses.

Where can I see it?: Found in igneous, & metamorphic rocks, particularly hydrothermal & volcanic rocks.

Fun Fact: ‘Amethyst’ derives from the Greek word ‘amethystos’, which means ‘not drunken’. The Greeks & Romans once believed amethyst protected people from intoxication.

Mineral: Almandine (a type of garnet)

Chemical Formula: Fe₃Al₂(SiO₄)₃

Description: Lustrous (shiny) crystals which are usually deep red with irregular surfaces. Well formed crystals look like footballs, due to their rhombic sides.

Formation: When sedimentary rocks, high in aluminium, are metamorphosed (subjected to high heat & pressure). Garnets also form in some igneous rocks.

Uses: Used as gemstones for jewellery & ornaments, and as industrial abrasives.

Where can I see it?: Found in many UK locations such as Fife, Aberdeen, and Cornwall.

Fun Fact: The name garnet is derived from the Latin word ‘garanatus’, meaning ‘seed-like’, because they look like pomegranate seeds.

Mineral: Chalcopyrite

Chemical Formula: CuFeS₂

Description: Golden yellow in colour, sometimes with a purple or pink tarnish. Metallic lustre and soft – it can be scratched with a knife.

Formation: Forms in sulphide deposits, in hydrothermal veins (igneous) or metamorphosed igneous rocks.

Uses: It is currently the main copper source globally, which is used in buildings, houses, and electrical appliances.

Where can I see it?: It can be seen all over Scotland & is found in veins running through a range of hydrothermal rocks.

Fun Fact: When oxidized, it forms other minerals like malachite, azurite, and cuprite.

Mineral: Malachite

Chemical Formula: Cu₂(CO₃)(OH)₂

Description: Bright to dark green colours in alternating circular and bubbly layers.

Formation: Forms around copper ore bodies, where the copper is weathered and oxidised.

Uses: Used for paint pigments, ornaments, jewellery, and tumble stones (collectable smooth edged minerals).

Where can I see it?: Malachite specimens have been collected in Great Orme, Wales, from one of the oldest copper mines in the world, now a visitor centre.

Fun Fact: Unlike the large majority of minerals and gemstones, malachite is always found in one colour; shades of green.

Mineral: Olivine

Chemical Formula: (Mg, Fe)₂SiO₄

Description: Green and glassy with irregular surfaces.

Formation: Olivine forms at very high temperatures in igneous rocks & is usually the first mineral to crystallise out of magma.

Uses: Forms the gemstone peridot, used in jewellery, and is also used in the steel & aluminium industries.

Where can I see it?: Found in many igneous rocks, such as peridotite, basalts and gabbros. Dunite (a rock composed of 90%+ olivine) can be found on the Isle of Skye.

Fun Fact: Is commonly seen in many extraterrestrial places, from the Moon and Mars, to asteroids and the outer layers of dust orbiting young stars.

Mineral: Amazonite

Chemical Formula: K(AlSi₃O₈)

Description: Green to blue-green in colour, possibly due to a high lead content. Sunlight can also enrich the colour of amazonite.

Formation: Amazonite forms when magma cools slowly, allowing large crystals to grow. We don’t know exactly the conditions required to make the green colour.

Uses: Commonly used in jewellery making and is cut in to beads and gemstones for use in necklaces, bracelets, rings, and earrings.

Where can I see it?: Found in many countries, including Canada, Australia, Namibia & India.

Fun Fact: Although amazonite is not sourced in the Amazon rainforest, its name is derived from its colour that resembles the lush greens and blues of the region.

Mineral: Biotite

Chemical Formula: K(Mg, Fe)₃(AlSi₃O₁₀)(F, OH)₂

Description: Biotite is a dark-coloured brown to black mica that forms in very thin, flaky sheets.

Formation: Forms in igneous and low grade metamorphic rocks.

Uses: Used to determine the age of rocks and geological features.

Where can I see it?: Found in many igneous and metamorphic rocks, it makes up 7% of the crust so is very common in the world and the UK.

Fun Fact: Biotite is sometimes referred as ‘the other fools gold’, as when the flakes are struck by sunlight in a gold pan, they can have a shiny gold appearance.

Mineral: Eudialyte

Chemical Formula: Na₁₅Ca₆Fe₃Zr₃Si(Si₂₅O₇₃)(O, OH, H₂O)₃(Cl, OH)₂

Description: Fine crystalline mineral, coloured dark pink to red-brown and purple.

Formation: Forms in alkaline igneous rocks.

Uses: A rare earth element ore with zirconium extracted from the ore used in jet engines and space shuttle parts. It is also used as gemstones for jewellery or for collecting.

Where can I see it?: Peralkaline igneous systems, with a lot of the research on this mineral having been done in Greenland and Russia.

Fun Fact: Eudialyte was only discovered in 1819 in Greenland and finding a well formed crystal is rare.

Mineral: Labradorite

Chemical Formula: (Ca, Na)Al(Al, Si)Si₂O₈

Description: Pale green to blue, colourless and grey-white; labradorite can display an iridescent optical effect known as labradorescence, where colours appear to change when viewed at different angles.

Formation:  Form from the cooling of magma deep inside the Earth. They often have large crystals.

Uses: Often used in jewellery for its unique colours. There are many spiritual uses.

Where can I see it?: Found in igneous rocks like basalt & anorthosite (an igneous rock in which labradorite can be the most abundant mineral). It is also seen in metamorphic rocks such as gneiss.

Fun Fact: Named after its location of discovery on the Isle of Paul, near Nain, Labrador.