Minerals & Crystals Guide

Quartz is the most abundant mineral on Earth's continental crust and one of the most recognizable minerals for rockhound…

Amethyst is the purple variety of quartz, colored by iron impurities and natural irradiation. It is the most valued quar…

Agate is banded chalcedony — microcrystalline quartz that forms in concentric layers inside volcanic vesicles (gas bubbl…

Jasper is opaque microcrystalline quartz, often containing mineral inclusions that create stunning patterns — landscapes…

Garnet is a group of closely related silicate minerals that share the same crystal structure but vary in chemical compos…

Pyrite — "fool's gold" — is actually one of the most treasured mineral specimens when well-crystallized. Perfect cubic c…

Fluorite is one of the most colorful and collectible minerals — a single specimen can display purple, green, yellow, and…

Calcite is the most stable polymorph of calcium carbonate and one of the most common minerals on Earth. It forms limesto…

Tourmaline is the chameleon of minerals — no other mineral species produces such a complete spectrum of colors in gem qu…

Beryl produces more coveted gemstones than any other mineral species. The Emerald Hollow Mine in North Carolina is the o…

Turquoise is one of the oldest gemstones, traded and treasured for 3,000+ years. The US Southwest produces the world's f…

Obsidian forms when silica-rich lava cools so rapidly that crystals cannot form — producing a natural volcanic glass. Gl…

Precious opal displays a spectacular color-play phenomenon called opalescence — brilliant flashes of spectral colors cau…

Sapphire is the gem variety of corundum (all non-red gem corundum is called sapphire). Montana is the only significant U…

Gold is one of the earliest materials worked by humans and still one of the most sought-after. In the US, the 1848 Calif…

Topaz is one of the hardest silicate minerals and produces beautiful gemstones. Texas has a unique situation — Mason Cou…

Malachite is a copper carbonate hydroxide that forms in the oxidation zones of copper deposits — particularly in the Ame…

Ammonites were shelled cephalopods (relatives of today's nautilus and octopus) that went extinct with the dinosaurs 66 m…

Labradorite is a feldspar mineral famous for its iridescent optical phenomenon — labradorescence — where light reflects …

Hematite is the most important iron ore mineral and has been used as a red pigment (red ochre) since prehistoric times. …

Selenite is the clear, bladed crystal variety of gypsum — one of the most common sulfate minerals. Mexico's Cave of the …

Natural citrine is rarer than amethyst, and most commercial "citrine" is actually heat-treated amethyst (heating purple …

Rose quartz is the pink variety of quartz, colored by trace amounts of titanium, iron, or manganese. Unlike most quartz,…

Petrified wood forms when buried plant material is replaced by silica-rich groundwater over millions of years — molecule…

Amazonite is a vivid blue-green variety of potassium feldspar (microcline) colored by trace lead and water impurities. C…

Rhodonite is a manganese silicate mineral famous for its striking rose-pink to crimson color, typically streaked with bl…

Rhodochrosite is a manganese carbonate mineral and Colorado's state mineral. The Sweet Home Mine near Alma, Colorado has…

The Oregon Sunstone is one of America's most unique gems — a labradorite feldspar containing copper platelets that creat…

Moonstone is an orthoclase feldspar that displays adularescence — a billowing blue to white glow that seems to float wit…

Azurite is one of the most intensely blue minerals in nature — a copper carbonate that forms alongside malachite in the …

Chrysocolla is a hydrated copper silicate that forms the most vivid blue-green colors found in copper deposits. The stan…

Spessartine is the manganese-rich member of the garnet group, producing the most vibrant orange to orange-red colors in …

Kyanite is one of mineralogy's most fascinating anomalies — its hardness varies dramatically depending on direction. Run…

Staurolite is famous for its cruciform (cross-shaped) twin crystals — called "fairy crosses" — that have been collected …

Iolite is the gem variety of cordierite, famous for its extraordinary trichroism — it shows blue-violet, yellow-grey, an…

Epidote is a calcium aluminum iron silicate mineral known for its distinctive pistachio-green color. Unakite — a popular…

Magnetite is the most magnetic of all naturally occurring minerals — lodestone (naturally magnetized magnetite) was used…

Galena is the primary ore of lead and one of the most abundant sulfide minerals. It's the official state mineral of Wisc…

Sphalerite is the primary ore of zinc and one of the most colorful sulfide minerals — ranging from pale yellow to honey …

Barite is the world's primary source of barium and is most familiar to collectors as "desert roses" — rosette-shaped cry…

Aragonite is a polymorph of calcite — same composition (CaCO₃), different crystal structure. It is the mineral in pearls…

Dolomite is a calcium magnesium carbonate and major rock-forming mineral. It's the principal mineral in dolostone (dolom…

Chalcopyrite is the world's most important copper ore mineral and produces the striking "peacock ore" that beginners oft…

Lepidolite is a lilac-pink lithium mica found in granitic pegmatites and is one of the most important lithium sources in…

Sodalite is a deep blue feldspathoid mineral often confused with lapis lazuli. Its vivid royal blue color with white cal…

Prehnite is an apple-green to pale green calcium aluminum silicate that fills vesicles (gas bubbles) in basaltic lava. N…

Spinel is one of history's most misunderstood gems — many of history's most famous "rubies" are actually spinels. The Bl…

Alexandrite is the color-change variety of chrysoberyl — one of the rarest and most valuable gemstones in the world. It …

Rutile is the most common titanium oxide mineral and is prized both as a titanium ore and as a collector mineral. Its be…

Dumortierite is a vibrant blue borosilicate mineral found in high-temperature metamorphic and granitic pegmatite environ…

Peridot is the gem variety of olivine, and Arizona's San Carlos Apache Reservation is one of the world's most important …