Many minerals are gray or metallic, but this list is for minerals that are black or nearly black. First, be sure you're looking at actual minerals (visible grains or crystal formations) with a black or nearly black color, not a smooth-textured black rock. Inspect the color closely, in good light, for greenish or brownish or bluish tinges. Try to identify the rock type (start with "How to Look at a Rock" and determine, or at least make your best guess, whether it's an igneous, sedimentary or metamorphic rock). That is important for many black minerals, which favor a particular rock class. Black minerals are relatively easy to identify once you've learned about the most common ones. See them here in alphabetical order, along with their typical luster and hardness.
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 (87° and 93°), the main way to distinguish it from hornblende. Luster glassy; hardness 5 to 6.
Lazurite under Creative Commons
Chromite is a chromium-iron oxide found in pods or veins in bodies of peridotite and serpentinite. It also may be segregated in thin layers near the bottom of large plutons, former bodies of magma. It may resemble magnetite, but it rarely forms crystals, is only weakly magnetic and has a brown streak. Luster submetallic; hardness 5.5.
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 in every case hematite produces a reddish streak. Luster dull to semimetallic; hardness 1 to 6.
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°). Crystals may be short or long, and even needlelike in amphibolite schists. Luster glassy; hardness 5 to 6.
Magnetite 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. Luster metallic; hardness 6.
wanderflechten under Creative Commons
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. Luster metallic to dull; hardness 2 to 6.
Graeme Churchard under Creative Commons
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. Luster metallic to adamantine; hardness 6 to 6.5.
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. Luster glassy; hardness 7 to 7.5.
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).