Mineral Pictures Index

If youre interested in rock collecting, you know that rocks you find in the real world rarely look like the polished specimens you see you rock shops or museums. In this index, youll find pictures of minerals like those youll most likely encounter in your expeditions. This list starts with the handful of common minerals called the rock-forming minerals, followed by the most common accessory minerals—youll find them scattered in many different rocks but seldom in large amounts. Next, youll see a set of rare or notable minerals, some of which are common in commercial rock shops. Finally, you can check out some special galleries designed to help you to identify your specimens. Rock-Forming Minerals Rock-forming minerals are among the most common (and least valuable) minerals in the world. They form the basis of igneous, metamorphic, and sedimentary rocks, and are used to classify and name rocks. Some examples include: Biotite—Black mica, common in igneous rocks. Calcite—The most common carbonate mineral, making up limestone. Dolomite—Magnesium-rich cousin to calcite. Feldspar—A group making up the most common mineral in the crust. (Feldspar Gallery) Hornblende—The most common mineral of the amphibole group. Muscovite—White mica, found in all kinds of rocks. Olivine—A green mineral found strictly in igneous rocks. Pyroxene—A group of dark minerals of igneous and metamorphic rocks. Quartz—Familiar as crystals and as noncrystalline chalcedony. (Quartz/Silica Gallery) Accessory Minerals   Accessory minerals may be included in any rock you pick up, but unlike rock-forming minerals, they are not a basic part of the rock. In other words, a rock must contain quartz, feldspar, and mica  in order to be classified as granite. If the rock also happens to contain the mineral titanite, the rock is still granite -- and the titanite is classified as an accessory mineral.  Accessory minerals are also not  particularly abundant, and so they may be more valuable than rock-forming minerals. Some examples include: Andalusite—Makes collectible crossed crystals. Anhydrite—What gypsum becomes deep underground. Apatite—The phosphate mineral making up teeth and bones. Aragonite—Calcites close carbonate cousin. Barite—A heavy sulfate sometimes found in roses. Bornite—Peacock ore copper mineral tarnishes a crazy blue-green. Cassiterite—Ancient and principal ore of tin. Chalcopyrite—Foremost ore of copper. Chlorite—The green mineral of many metamorphic rocks. Corundum—Natural alumina, sometimes known as sapphire and ruby. Epidote—Metamorphic mineral of a pistachio/avocado green color. Fluorite—Every rockhound has a piece of this soft, colorful mineral. Galena—A heavy, glittering mineral, principal ore of lead metal. Garnet Almandine—The true garnet-red garnet mineral. Andradite—Green crystals from central California. Grossular—A greenish garnet illustrated by a well-formed crystal. Pyrope—Wine-colored grains in a California eclogite. Spessartine—A honey-colored set of crystals from China. Uvarovite—Emerald-green crystals from Russia. Goethite—The brown oxide mineral of soils and iron ore. Graphite—The stuff of pencils has more rugged uses too. Gypsum—Shown in its prettiest form, desert roses. Halite—Also known as rock salt, this evaporite mineral sits at your table. Hematite—Iron oxide mineral of many forms including this kidney ore. Ilmenite—Black titanium ore lurks in heavy sands. Kyanite—A sky-blue mineral formed by high-pressure metamorphism. Lepidolite—Lithium mica mineral with a fine lilac color. Leucite—Feldspathoid mineral also called white garnet. Magnetite—Magnetic iron oxide also known as lodestone. Marcasite—Close crystal cousin of pyrite. Nepheline—Feldspathoid mineral well known to potters. Phlogopite—Brown mica mineral closely related to biotite. Prehnite—Bottle-green mineral of low-grade metamorphic rocks. Psilomelane—Manganese oxides make up this black crusty mineral. Pyrite—Fools gold and the most important sulfide mineral. Pyrolusite—The black manganese mineral of dendrites. Rutile—Needles of this oxide mineral occur in many rocks. Serpentine—The group of green minerals that yields asbestos. Sillimanite—Indicator mineral for high grades of metamorphism. Sphalerite—The major zinc ore and an interesting mineral. Spinel—Rugged oxide mineral of metamorphosed limestones. Staurolite—A typical crossed pair of crystals in a mica schist matrix. Talc—The softest mineral of them all. Tourmaline—The common black variety called schorl. Zeolites—Group of low-temperature minerals with many industrial uses. Zircon—Both a gemstone and a precious source of geologic information. Uncommon Minerals and Varieties This collection of minerals includes metals, ores, and gems. Some of these -- gold, diamond, and beryl for example -- are among the most valuable and coveted minerals in the world. If you find these in your rock hunting excursions, be sure to keep them safe. Some examples include: Amethyst—The purple form of crystalline quartz. Axinite—Minor silicate of striking crystal form and color. Benitoite—Very blue, very rare and weird ring silicate mineral. Beryl—Gemstone of many names, including emerald. Borax—This household commonplace is mined in desert lakebeds. Celestine—Pale, sky-blue strontium carbonate. Cerussite—Spiky gray lead carbonate. Chrysocolla—Bright green-blue mineral found near copper ore. Cinnabar—Lipstick-red mineral and major ore of mercury. Copper—Native metal shown in its natural wiry form. Cuprite—Red copper ore and sometimes spectacular specimen stone. Diamond—Natural diamond crystal from the Congo. Dioptase—Bright-green crystalline sign of copper deposits. Dumortierite—Blue boron mineral of gneisses and schists. Eudialyte—Striking red vein-maker in nepheline syenites. Fuchsite—Chromium colors this mica mineral a flashy green. Gold—The native metal shown in an Alaskan nugget. Hemimorphite—Handsome pale crusts of hydrous zinc silicate. Herkimer Diamond Quartz—Doubly terminated crystals from New York. Labradorite—The butterfly of the feldspars has dazzling blue schiller. Lazurite—Ancient mineral source of ultramarine pigment. Magnesite—Magnesium carbonate ore mineral. Malachite—Ultra-green copper carbonate, a favorite mineral of carvers. Molybdenite—Soft metallic mineral and ore of molybdenum. Opal—Precious silica mineraloid may display a rainbow of colors. Platinum—Rare crystalline nuggets of the native metal. Pyromorphite—Flashy green lead phosphate mineral. Pyrophyllite—Soft mineral closely resembling talc. Rhodochrosite—Calcites manganese cousin with distinctive rosy color. Ruby—Deep-red gemmy variety of corundum. Scapolite—Streaked clear crystals of metamorphosed limestones. Siderite—Brown iron carbonate mineral. Silver—Wiry specimen of the rare native metal. Smithsonite—Carbonate of zinc appears in many forms. Sodalite—Deep blue feldspathoid and a rock carvers staple. Sulfur—Delicate crystals accumulate around a volcanic vent. Sylvite—Red potassium mineral distinguished by its bitter taste. Titanite—Collectible brown crystalline mineral once known as sphene. Topaz—Hardness and good crystals make it a popular mineral. Turquoise—The most precious phosphate mineral. Ulexite—One of many borate minerals, ulexite forms the unique TV rock. Variscite—This phosphate comes in veins like slabs of green candy. Willemite—Prized by collectors for its bright fluorescence. Witherite—Scarce barium carbonate mineral. Tools for Identifying Minerals It isnt always easy to identify minerals, even if theyre fairly common. Fortunately, there are tools used by geologists to aid in identification. Special tests for luster and streak can help; so too can these galleries of relatively common minerals of different colors. Black Minerals Blue and Purple Minerals Brown Minerals Green Minerals Red and Pink Minerals Yellow Minerals Mineral Habits Mineral Lusters Mineral Streak Mineraloids