KEY TO THE MINERALS, BASED ON HARDNESS, COLOR, ETC.

OPAQUE COLORS
Color Hardness Streak Remarks Mineral
Red
scarlet 2.5 scarlet surface tarnishes black [prousite]
2.5 vermilion surface scarlet to dark red [cinnabar]
ochre 7 white non-crystalline [jasper]
6 ochre red color red to almost black [hematite]
rose 4 white effervesces in warm acid [rhodochrosite]
dark 4 orange [zincite]
2.5 purplish red surface tarnishes black [pyrargyrite]
brownish 3.5 brownish red [cuprite]
Orange 3.5 white to yellowish [pyromorphite]
1-1½ orange [realgar]
Blue 5.5-6 white in igneous rocks [sodalite]
azure 4 azure [azurite]
sky 7 & 4.5 white blade-like crystals [cyanite]
turquoise 6 blue non-crystalline [turquois]
2-4 white [chrysocolla]
Green
malachite 3.5 lighter green [malachite]
olive 6.5-7 white in igneous rocks [olivine]
3.5 white to yellow [pyromorphite]
2 white mica-like cleavage [chlorite]
1 white greasy feel, color light to dark olive green [talc]
yellowish 6.5 white [epidote]
2.5-4 white color yellow green to olive [serpentine]
Yellow
golden 2.5 shining non-crystalline [gold]
brassy 6 greenish-black usually crystalline [pyrite]
6 greenish-gray color pale brassy yellow, usually non-crystalline [marcasite]
5.5 greenish-black colors nitric acid green [millerite]
4 greenish-black color golden similar to gold [chalcopyrite]
3.5 dark brown purplish tarnish on surface [tetrahedrite]
bronze 5.5 pale brownish-black color with coppery cast [niccolite]
4 dark gray-black with speedy black tarnish [pyrrhotite]
3 gray-black brownish with bluish tarnish [bornite]
2.5 shining coppery red color [copper]
sulphur 3.5 white to yellowish compact masses [pyromorphite]
2 yellow [sulphur]
1-3 earthy masses [carnotite]
Brown
violet 1½ shining tarnishes black [cerargyrite]
yellowish 7.5 white 4-sided prisms [zircon]
6.5 gray [cassiterite]
5.5 ochre yellow compact to earthy masses [limonite]
5 brownish-yellow [goethite]
4.5 black [wolframite]
3.5 yellowish-brown [sphalerite]
3.5 white [siderite]
grayish 7.5 white often twinned [staurolite]
6.5 pale brown [rutile]
3.5 white to yellowish earthy masses [pyromorphite]
reddish 7 white dodecahedrons & trapezohedrons [garnet]
Black 6.5 gray [cassiterite]
6 reddish-brown [franklinite]
6 black magnetic [magnetite]
5.5 dark brown [chromite]
5.5 black yellow precipitate in sulphuric acid [wolframite]
5-6 black non-magnetic [ilmenite]
5-6 brownish-black compact masses [psilomelane]
5 brownish-yellow surface often brownish [goethite]
3.5 dark brown tetrahedrons [tetrahedrite]
2.5 silvery fresh surfaces silver color [silver]
2.5 scarlet fresh surfaces bright red [prousite]
2.5 purplish red fresh surfaces red [pyrargyrite]
2 black earthy masses [pyrolusite]
1 steel gray greasy feel [graphite]
Metallic Gray 2.5 black tarnishes black, bluish, or green [chalcocite]
2.5 lead gray sectile [argentite]
2.5 lead gray cubic cleavage [galena]
2 lead gray long prismatic crystals [stibnite]
1.5 bluish gray in scales [molybdenite]
steel 5.5 gray black rose color in nitric acid [smaltite]
4.5 steel gray very heavy [platinum]
4 reddish black often in striated prisms [manganite]
1 gray with greasy feel [graphite]
silvery 5.5 black [arsenopyrite]
2.5 silvery tarnishes black on exposure [silver]
reddish 5.5 gray black rose color in nitric acid [cobaltite]
pearly 1-1½ shining exposed surfaces violet brown [cerargyrite]
White, with impurities 4 white porcelainous masses, effervesces in acid [magnesite]
grayish or yellowish 2 white earthy masses, greasy feel [kaolinite]
1-3 white earthy masses [bauxite]
1 white greasy feel, fibrous or scaly [talc]
TRANSPARENT OR TRANSLUCENT COLORS
Color Hardness Remarks Mineral
Colorless or with faint tinges of color due to impurities
10 in octahedrons [diamond]
9 in hexagonal prisms [corundum]
8 in hexagonal prisms [topaz]
7 in three-sided prisms [tourmaline]
7 in hexagonal prisms [quartz]
7 non-crystalline [chalcedony]
7 or 4.5 cubes with beveled edges [boracite]
6 non-crystalline, pearly luster [opal]
5.5 rhombohedrons [willemite]
5.5 trapezohedrons [analcite]
5.5 tufts of needle-like crystals [natrolite]
5.5 sheaf-like bundles of crystals [stilbite]
5 hexagonal prisms with basal cleavage [apatite]
5 effervesces in acid [smithsonite]
5 becomes jelly-like in acid [calamine]
4.5 monoclinic prisms [colemanite]
4 in cubes [fluorite]
3.5 effervesces in acid, but one cleavage [aragonite]
3.5 effervesces in acid, heavy [cerrusite]
3 effervesces in acid, rhomboidal cleavage [calcite]
3 no effervescence, but soluble in nitric acid [anglesite]
2.5 in cubes tastes of salt [halite]
2 soluble in water, sweetish taste [borax]
2 1 perfect cleavage, and two imperfect cleaves at 66 with each other [gypsum]
White or with faint tinges of color due to impurities, such as pink, bluish, etc.
7 hexagonal prisms [quartz]
7 non-crystalline [chalcedony]
7 or 4.5 cubes with beveled edges [boracite]
6 non-crystalline, pearly luster [opal]
6 cleavage in 3 directions, good in 2 and imperfect in the other [feldspar]
5.5 short eight-sided prisms [pyroxene]
5.5 long six-sided prisms [amphibole]
5.5 trapezohedrons [analcite]
5.5 tufts of needle-like crystals [natrolite]
5.5 sheaf-like bundles of crystals [stilbite]
5.5 rhombohedrons [willemite]
5 effervesces in acid [smithsonite]
5 becomes jelly-like in acid [calamine]
4.5 & 7 cubes with beveled edges [boracite]
4.5 monoclinic prisms [colemanite]
4 effervesces in acid, porcelainous [magnesite]
3.5-4 effervesces in acid, heavy, red color in flame [strontianite]
3.5 effervesces in acid, heavy, green color in flame [witherite]
3.5 effervesces in warm acid, rhomboidal cleavage [dolomite]
3.5 effervesces in acid, cleavage in one direction only [aragonite]
3.5 effervesces in acid, heavy, does not color flame [cerrusite]
3-3.5 no effervescence, cleavage in three directions at right angles [anhydrite]
3 effervesces in acid, rhomboidal cleavage [calcite]
3 tabular crystals, heavy, green color in flame [barite]
2-3 cleaves in thin elastic sheets [mica]
2.5 cleaves in cubes [cryolite]
2.5 cubes, soluble in water, salty taste [halite]
2 1 perfect cleavage, and 2 less perfect ones [gypsum]
2 cleaves in thin non-elastic sheets [chlorite]
2 soluble in water, tastes sweet [borax]
1 greasy feel [talc]
Green 9 hexagonal prisms [oriental emerald]
8 octahedrons [spinel]
7.5 hexagonal prisms [beryl]
7 three-sided prisms [tourmaline]
7 dodecahedrons or trapezohedrons [garnet]
7 non-crystalline [prase] or [plasma]
6.5-7 non-crystalline, olive color [olivine]
6.5 yellow green color, rather opaque [epidote]
6 non-crystalline, pearly luster [opal]
5.5 short eight-sided prisms [pyroxene]
5.5 long six-sided prisms [amphibole]
5 hexagonal prisms [apatite]
4 cubes [fluorite]
3.5 effervesces in acid [cerrusite]
2.5-4 somewhat greasy feel, massive or fibrous [serpentine]
2 in mica-like scales, non-elastic [chlorite]
1 greasy feel, fibrous or scaly [talc]
Red 9 hexagonal prisms [ruby]
8 octahedrons [spinel]
7 three-sided prisms [tourmaline]
7 dodecahedrons or trapezohedrons [garnet]
7 hexagonal [rose quartz]
7 non-crystalline [jasper] or [carnelian]
6 pearly luster [fire opal]
4 cubes, rose tints [fluorite]
2-3 pink mica-like scales [lepidolite]
Blue 9 hexagonal prisms [sapphire]
7 & 4.5 blade-like crystals [cyanite]
6 non-crystalline masses [turquois]
5.5-6 in igneous rocks [sodalite]
4 azure color [azurite]
3.5 effervesces in acid, heavy [cerrusite]
2-4 earthy masses, turquoise color [chrysocolla]
Violet 7 hexagonal prisms [amethyst]
4 cubes [fluorite]
Yellow 9 hexagonal prisms [oriental topaz]
8 octahedrons [spinel]
8 hexagonal prisms [topaz]
4 cubes [fluorite]
Brown 9 hexagonal prisms [corundum]
8 octahedrons [spinel]
7.5 four-sided prisms [zircon]
7 hexagonal prisms [smoky quartz]
7 three-sided prisms [tourmaline]
7 non-crystalline [flint]
6 non-crystalline [opal]
5.5 short eight-sided prisms [pyroxene]
5.5 long six-sided prisms [amphibole]
2-3 cleaves into thin sheets [mica]
Black 9 hexagonal prisms [corundum]
8 octahedrons [spinel]
7 three-sided prisms [tourmaline]
5.5 short eight-sided prisms [pyroxene]
5.5 long six-sided prisms [amphibole]
2-3 cleaves in thin sheets [mica]