How to Identify Black Minerals

Pure black minerals are less common than other types of minerals, and they can be difficult to recognize. But by carefully observing such things as grain, color, and texture, you can easily identify many black minerals. This list will help you identify the most significant of them, along with notable geological characteristics, including luster and hardness as measured on the Mohs Scale.

Augite
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Augite is the usual black or brownish-black pyroxene mineral of the dark igneous rocks and some high-grade metamorphic rocks. Its crystals and cleavage fragments are nearly rectangular in cross section (at angles of 87 and 93 degrees). This is the main way to distinguish it from hornblende, which is discussed later in this list.

Glassy luster; hardness of 5 to 6. More »

Biotite
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This mica mineral forms shiny, flexible flakes of a deep black or brownish-black color. Large book crystals occur in pegmatites and it is widespread in other igneous and metamorphic rocks; tiny detrital flakes may be found in dark sandstones.

Glassy to pearly luster; hardness of 2.5 to 3. More »

Chromite
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Chromite is a chromium-iron oxide found in pods or veins in bodies of peridotite and serpentinite. It may also be segregated in thin layers near the bottom of large plutons, or former bodies of magma, and is sometimes found in meteorites. It may resemble magnetite, but it rarely forms crystals, is only weakly magnetic and has a brown streak.

Submetallic luster; hardness of 5.5. More »

Hematite
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Hematite, an iron oxide, is the most common black or brownish-black mineral in sedimentary and low-grade metasedimentary rocks. It varies greatly in form and appearance, but all hematite produces a reddish streak.

Dull to semimetallic luster; hardness of 1 to 6. More »

Hornblende
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Hornblende is the typical amphibole mineral in igneous and metamorphic rocks. Look for glossy black or dark green crystals and cleavage fragments forming flattened prisms in cross section (corner angles of 56 and 124 degrees). Crystals may be short or long, and even needle-like in amphibolite schists.

Glassy luster; hardness of 5 to 6. More »

Ilmenite
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Crystals of this titanium-oxide mineral are sprinkled in many igneous and metamorphic rocks, but they're sizeable only in pegmatites. Ilmenite is weakly magnetic and produces a black or brownish streak. Its color can range from dark brown to red.

Submetallic luster; hardness of 5 to 6. More »

Magnetite
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Magnetite or lodestone is a common accessory mineral in coarse-grained igneous rocks and metamorphic rocks. It may be gray-black or have a rusty coating. Crystals are common, with striated faces, and shaped in octahedrons or dodecahedrons. The streak is black, but its strong attraction to a magnet is the surefire test. 

Metallic luster; hardness of 6. More »

Pyrolusite
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These manganese-oxide minerals usually form massive ore beds or veins. The mineral forming black dendrites between sandstone beds is typically pyrolusite; crusts and lumps are typically called psilomelane. In all cases, ​the streak is sooty black. It releases chlorine gas in hydrochloric acid.

Metallic to dull luster; hardness of 2 to 6. More »

Rutile
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The titanium-oxide mineral rutile usually forms long, striated prisms or flat plates, as well as golden or reddish whiskers inside rutilated quartz. Its crystals are widespread in coarse-grained igneous and metamorphic rocks. Its streak is light brown.

Metallic to adamantine luster; hardness of 6 to 6.5. More »

Stilpnomelane
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This uncommon glittering black mineral, related to the micas, is found primarily in high-pressure metamorphic rocks with high iron content like blueschist or greenschist. Unlike biotite, its flakes are brittle rather than flexible.

Glassy to pearly luster; hardness of 3 to 4. More »

Tourmaline
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Tourmaline is common in pegmatites; it also is found in coarse-grained granitic rocks and some high-grade schists. It typically forms prism-shaped crystals with a cross-section shaped like a triangle with bulging sides. Unlike augite or hornblende, tourmaline has poor cleavage. It's also harder than those minerals. Clear and colored tourmaline is a gemstone; the typical black form is also called schorl.

Glassy luster; hardness of 7 to 7.5. More »

Neptunite
Neptunite. De Agostini/A. Rizzi/Getty Images

Uncommon Black minerals include allanite, babingtonite, columbite/tantalite, neptunite, uraninite, and wolframite. Many other minerals may occasionally take on a black color, whether they are ordinarily green (chlorite, serpentine), brown (cassiterite, corundum, goethite, sphalerite) or other colors (diamond, fluorite, garnet, plagioclase, spinel). More »