Grey crystals

Grey crystals get their colour from trace metals and light-scattering defects rather than from one shared mineral: 44 different stones read grey here, Amethyst, Ammonite and Angelite among them. Colour is the least reliable way to name a stone, so every entry carries the test that settles it.

• Amethyst7 Mohs · quartz · third-eye, crownQuartz stained violet by iron and buried radiation, quarried in geodes the size of coffins from Brazilian and Uruguayan basalt. It was a ca…
• Ammonite3.5-4.5 Mohs · organic · root, crownA cephalopod that built its shell in a logarithmic spiral, lived in the last chamber and used the rest for buoyancy, then went extinct with…
• Angelite3.5 Mohs · sulfate · throat, third-eye, crownAnhydrite, calcium sulfate with the water taken out, in a soft periwinkle from Peru, given a marketing name in the 1980s and now permanentl…
• Apache Tears5-6 Mohs · volcanic glass · root, heartObsidian nodules that survived when the surrounding glass hydrated into crumbly perlite, mineralogists call them marekanite. The American n…
• Astrophyllite3-4 Mohs · silicate · crown, third-eye, solar-plexusGreek for 'star leaf', and correctly so: a rare titanium silicate that grows in bronze blades radiating from a point, found in alkaline ign…
• Bismuth2-2.5 Mohs · man-made · crown, third-eyeElemental bismuth, grown in a saucepan and cooled slowly enough that the edges outrun the faces and produce those stepped rainbow labyrinth…
• Black Kyanite4.5-7 Mohs · silicate · root, throatIron-darkened kyanite from Brazil, growing in splayed fans that the trade decided look like a witch's besom and priced accordingly. It beha…
• Black Obsidian5-6 Mohs · volcanic glass · rootLava that cooled too fast to organise itself into crystals, a natural glass, and the sharpest edge available to any pre-metal culture. Meso…
• Blue Kyanite4.5-7 Mohs · silicate · throat, third-eyeAn aluminium silicate that forms only at high pressure deep in the crust, so its presence in a rock tells a geologist how far down it has b…
• Botswana Agate6.5-7 Mohs · chalcedony · crown, sacralGrey and dusty-pink banded agate from the Bobonong district, famous for band-per-millimetre fineness that makes cut slabs look like topogra…
• Bumblebee Jasper3-5 Mohs · rock (aggregate) · solar-plexus, sacralNot a jasper at all: banded calcite and anhydrite laced with native sulfur and arsenic sulfides, deposited in a fumarole near Papandayan vo…
• Celestite3-3.5 Mohs · sulfate · throat, third-eye, crownStrontium sulfate, the mineral that makes fireworks red, growing as pale blue crystal-lined cavities in Madagascan and Ohioan sedimentary r…
• Crazy Lace Agate6.5-7 Mohs · chalcedony · solar-plexus, sacralChihuahuan agate that formed in a rock that kept breaking and re-healing, producing banding with no discipline whatsoever. Dealers call it …
• Desert Rose2-3.5 Mohs · sulfate · root, crownGypsum crystallising out of evaporating groundwater in a desert basin, growing around and through the sand until it forms a rosette. Oklaho…
• Galena2.5-2.75 Mohs · sulfide · rootLead sulfide in perfect silver cubes, the principal ore of lead, the source of Roman plumbing, Egyptian kohl and a great deal of historical…
• Green Aventurine6.5-7 Mohs · quartz · heartA quartzite glittering with chromium mica, mined chiefly in southern India and sold in more starter kits than almost anything else. The nam…
• Hematite5.5-6.5 Mohs · oxide · rootIron oxide, the mineral that makes Mars red and rust red, named from the Greek for blood because of the streak it leaves. Polished it looks…
• Howlite3.5 Mohs · silicate · crown, third-eyeA calcium borosilicate from Nova Scotia that would be an obscure collector's mineral if it were not the perfect blank canvas, porous, white…
• Iolite7-7.5 Mohs · silicate · third-eye, throatCordierite, transparent and violet-blue, and famous for a story that may well be true: thin slices act as a polarising filter, and there is…
• Labradorite6-6.5 Mohs · feldspar · third-eye, throat, crownA grey plagioclase feldspar whose internal layering is spaced at exactly the wavelength of visible light, so it throws aurora colours from …
• Lepidolite2.5-3 Mohs · silicate · heart, third-eye, crownA lithium-bearing mica in lavender flakes, mined chiefly as a lithium ore and sold as a calming stone on the strength of that chemistry. Th…
• Magnesite3.5-4.5 Mohs · carbonate · crown, heartMagnesium carbonate, mostly an industrial refractory mineral, and the second great blank canvas of the crystal trade. Where howlite has bla…
• Milky Quartz7 Mohs · quartz · crownThe plain white filler of a thousand mineral veins, quartz clouded to opacity by trapped water and gas. It is the most abundant gemmy rock …
• Moonstone6-6.5 Mohs · feldspar · sacral, third-eye, crownPotassium feldspar that unmixed into microscopically thin alternating layers as it cooled, scattering light into a floating blue-white glow…
• Nephrite Jade6-6.5 Mohs · silicate · heartThe jade of ancient China, Māori Aotearoa and neolithic Europe, an amphibole so tough that stone-age cultures made axes of it before anyone…
• Ocean Jasper6.5-7 Mohs · chalcedony · heart, throatNot really a jasper: an orbicular rhyolite from the north-west Madagascan coast in which silica-rich fluids grew spherulites and then repla…
• Optical Calcite3 Mohs · carbonate · crown, third-eyeClear calcite that splits light into two rays, so text read through it appears twice, the mineral that let nineteenth-century physicists pr…
• Petrified Wood6.5-7 Mohs · organic · rootWood in which every cell wall was templated and then replaced by silica, molecule by molecule, so the structure survives while none of the …
• Phantom Quartz7 Mohs · quartz · third-eye, crownA crystal that stopped growing, got dusted with chlorite or iron, and then resumed, leaving its own younger outline sealed inside like a fo…
• Picture Jasper6.5-7 Mohs · chalcedony · root, third-eyeVolcanic ash and mud laid down in still water, compressed, silicified, and then sliced, so the desert scene you are looking at is an actual…
• Pietersite6.5-7 Mohs · quartz · third-eye, solar-plexusTiger's eye that was shattered by tectonics and healed back together at every angle at once, so the light in it looks like weather. Found i…
• Prehnite6-6.5 Mohs · silicate · heart, solar-plexusThe first mineral ever named after a person, Colonel Hendrik von Prehn, who brought it back from the Cape in the 1780s. It grows as pale gr…
• Pyrite6-6.5 Mohs · sulfide · solar-plexus, rootIron sulfide that grows in perfect cubes with striated faces, and has been fooling prospectors so reliably that its nickname is older than …
• Red Jasper6.5-7 Mohs · chalcedony · rootSilica clouded opaque with iron oxide, the plainest, oldest, most universally available amulet material on earth, worked from the Nile to t…
• Rutilated Quartz7 Mohs · quartz · solar-plexus, crownQuartz that trapped needles of titanium dioxide as it grew, producing what looks like gold wire frozen mid-flight. Renaissance Europeans ca…
• Septarian3-4 Mohs · rock (aggregate) · root, solar-plexusA mud concretion that formed around decaying organic matter on a Cretaceous seafloor, dried, cracked from the inside out, and then had ever…
• Seraphinite2-2.5 Mohs · silicate · heart, crownA compact chlorite from the Korshunovskoye iron skarn in Irkutsk Oblast, marketed since the 1990s under a name taken from the seraphim beca…
• Serpentine2.5-6 Mohs · silicate · heart, rootThe rock that forms when seawater cooks peridotite deep in the crust, California's state rock, the world's asbestos problem, and the crysta…
• Shiva Lingam6-7 Mohs · rock (aggregate) · root, sacral, crownCryptocrystalline quartz cobbles from one stretch of the Narmada river in Madhya Pradesh, collected annually under ancestral rights by spec…
• Shungite3.5-4 Mohs · organic · rootA roughly two-billion-year-old carbon rock from the Lake Onega region of Karelia, containing genuine fullerenes, the only significant natur…
• Smoky Quartz7 Mohs · quartz · rootOrdinary quartz darkened over geological time by natural radiation acting on trace aluminium, a stone that is literally a record of the rad…
• Snowflake Obsidian5-6 Mohs · volcanic glass · root, crownObsidian caught in the act of devitrifying, the white flowers are cristobalite crystals nucleating in glass that is slowly, over geological…
• Sodalite5.5-6 Mohs · silicate · throat, third-eyeA feldspathoid, mined in quantity in Ontario after a 1901 find was used to decorate Marlborough House for Princess Margaret of Connaught, h…
• Tiger's Eye6.5-7 Mohs · quartz · solar-plexus, rootBlue asbestos fibres replaced molecule by molecule with silica, keeping the fibrous alignment and gaining a hard glassy body, the sheen is …

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