Mineral Identification Key

The Mineral Identification Key

Copper, Michigan, Seaman Museum specimen

Table IIIB-2: Nonmetallic Luster; Hardness 7 to 10; Cleavage not prominent.. (Can not be scratched by quartz.) [Previous Table]

Hardness Color Luster Name System Habit SG Notes

6 to 7 Black to Dark-brown, may also be Yellowish-grey, more rarely Red, White or Colorless Adamantine to metallic in crystals, greasy on fracture surfaces, may be earthy or submetallic in botryoids, concretions, and massive forms CASSITERITE
(Rutile Group)
SnO₂ Tetragonal Usually massive as botryoidal crusts or concretions ("wood tin"), crystals usually short prismatic and complexly twinned producing unusual shapes ("knees", stubby five-pointed "stars," etc.) 6.8 to 7.1

6½ to 7 Grey to Bluish-grey, Brown to Honey-brown or Yellow to Golden-brown, more rarely Green or Violet Vitreous to sub-vitreous FERRO-AXINITE/
MANGANAXINITE
Ca₂FeAl₂BSi₄O₁₅(OH)
Ca₂MnAl₂BSi₄O₁₅(OH) Triclinic Usually as thin wedge-shaped "axhead" crystals, often arranged in rosettes 3.23 to 3.32 (ferro-), 3.30 to 3.36 (mangan-) End members difficult to distinguish, though low end and high end S.G. may do the trick. Magnesio-axinite and tinzenite are two rare related species.

6½ to 7 Pale-yellow to Olive-green to Olive-brown, Black Vitreous to sub-vitreous (forsterite) or submetallic to dull (fayalite) FAYALITE/
FORSTERITE
(Olivine Group)
Fe₂(SiO₄)
Mg₂(SiO₄) Orthorhombic Usually as crystalline massive or granular, crystals short-prismatic 4.39 (fayalite) to 3.24 (forsterite) End members distinguished by S.G. and luster. "Peridot" is the name for gem material in the fayalite-forsterite series, usually forsterite. Names for intermediate members of the series, such as "chrysolite" and "hortonolite" are based on chemical composition and should not be used unless the composition is known.

Hardness Color Luster Name System Habit SG Notes

6½ to 7 Colorless to White, more rarely Pale-yellow, Pale-pink or Pale-brown Vitreous BERTRANDITE
Be₄Si₂O₇(OH)₂ Orthorhombic Usually as tiny to micro tabular crystals, also granular aggregates 2.57 to 2.63 Usually associated with beryl in pegmatites. May exhibit basal and prismatic cleavages.

7 Colorless, Milky, Smoky-grey to Black, Amethyst, Rose, Yellow to Brownish-yellow, may be tinted other shades by inclusions Vitreous QUARTZ
(Crystalline)
SiO₂ Trigonal Usually in pyramidally terminated prismatic hexagonal crystals or glassy massive, "rock crystal," "smoky" and "amethyst" varieties may be very large, "citrine" usually small to medium in size, "rose" usually rather small to micro-scale 2.65 Abundant! in milky and massive forms. Common in rock crystal, smoky and amethyst forms, citrine rare, rose crystals very rare. (See also immediately below for crypto- and non-crystalline forms.)

Hardness Color Luster Name System Habit SG Notes

7 Colorless, Milky, Grey to Black, Red, Yellow to Brownish-yellow, Brown, Green, Blue, may be tinted other shades by inclusions Vitreous to waxy to dull QUARTZ
(Crypto- and Non-crystalline)
SiO₂ Trigonal "Chalcedony" as cryptocrystalline fibrous amorphous to sub-botryoidal masses, un-banded or un-patterned, with a waxy luster ("carnelian" is red, "chrysoprase" is green due to nickel, "heliotrope" or "bloodstone" is green with small red jasper flecks in it, "sard" is brown); "chalcedony, sub-variety agate" in circular, concentrically banded to intricately patterned masses with considerable color variation in single samples, waxy to vitreous luster; "chalcedony sub-variety onyx" has parallel layers instead of concentric ones ("sardonyx" has alternating white and black layers). 2.65 In massive, non- crystalline forms: "Jasper" red or blue, rarely yellow, dull luster; "flint" dark grey to black, dull to sub-vitreous luster; "chert" medium to light grey, dull to sub-vitreous luster; "aventurine" green due to inclusions, vitreous luster.

Hardness Color Luster Name System Habit SG Notes

7 Colorless, Milky-white, Pale-grey, Yellowish, and Brownish Vitreous CRISTOBALITE
SiO₂ Tetragonal (pseudo Isometric) Usually as micro-spherical aggregates, may be botryoidal or stalactic, crystals very rare, usually micro-octahedra 2.2 to 2.33 Largely restricted to siliceous volcanic rocks. Cristobalite is only partially stable at typical terrestrial temperatures, inverting to quartz. Most finds are actually quartz pseudomorphs of the original crystals

7 Colorless, Milky-white Vitreous TRIDYMITE
SiO₂ Orthorhombic & Hexagonal Usually as thin to thick tabular or twinned pseudo-hexagonal crystals 2.26 to 2.33 Largely restricted to felsic volcanic rocks; Tridymite is only partially stable at typical terrestrial temperatures, inverting to quartz. Most finds are actually quartz pseudomorphs of the original crystals

7 to 7½ Black to Bluish-black or Brownish-black or Greenish-black Vitreous to sub-vitreous, may appear somewhat oily on fracture surfaces SCHORL /
UVITE
(Tourmaline Group)
NaFe₃Al₆ (BO₃)₃(Si₆O₁₈)(OH)₄
(Ca,Na)(Mg,Fe)₃Al₅Mg(BO₃)₃(Si₆O₁₈)(OH,F)₄ Trigonal Schorl usually in stout to long-prismatic six-sided crystals with a nearly triangular cross-section. Uvite usually in stubby short-prismatic crystals, sometimes appearing almost pyramidal or dipyramidal, but may take identical habits. Both may also be massively crystalline or granular. 3.13 (schorl)
2.96 to 3.06 (uvite) These two end members are best distinguished by their S.G.s. Foitite, feruvite, and povondrite are three rare to very rare black Tourmaline Group members.

Hardness Color Luster Name System Habit SG Notes

7 to 7½ Black to Brownish-black or Brown Vitreous to sub-vitreous, may appear oily on fracture surfaces DRAVITE
(Tourmaline Group)
NaMg₃Al₆(BO₃)₃(Si₆O₁₈)(OH)₄ Trigonal Usually as stout prismatic six-sided crystals, often with a pyramidal termination at one end and a pedial termination at the other 2.9 to 3.3 Largely restricted to marbles, schists and slates. Best distinguished from schorl and uvite by environment when black. Buergerite is a rare bronze-brown Tourmaline Group member.

7 to 7½ Dark emerald-green to Greenish-black to Black Vitreous, may appear oily on fracture surfaces CHROMEDRAVITE
(Tourmaline Group)
NaMg₃(Cr,Fe)₆ (BO₃)₃ (Si₆O₁₈)(OH)₄ Trigonal Usually as small to tiny nearly equant short-prismatic crystals and grains 3.39 to 3.40 Usually distinguished by its deep emerald green color – largely restricted to chromium bearing micaceous metasomatites. Very rare. Distinguished from dark greenish-black schorl or uvite by its higher S.G

7 to 7½ Light- to Medium-green, Pink to Red, Light- to Medium-blue to Dark-blue, more rarely Light-brown to Yellow, Colorless Vitreous to oily ELBAITE
(Tourmaline Group)
Na(Li,Al)₃Al₆ (BO₃)₃(Si₆O₁₈)(OH)₄ Trigonal Usually in slender prismatic six-sided crystals with a nearly triangular cross-section, often appearing somewhat rounded. Whole crystals may be hemimorphic, with different shaped terminations (pyramidal and pedial) at opposite ends 3.05 to 3.10 Distinguished from most other Tourmaline Group species by its lighter colors – also, largely restricted to granite-pegmatites. Dark-blue elbaite is almost impossible to distinguish from dark blue schorl, and both can occur together. Olenite, pale pink, and liddicoatite, light-pink or light-green, are two rare to very rare colored Tourmaline Group species.

Hardness Color Luster Name System Habit SG Notes

7 to7½ Deep-green to "Rusty"-green Vitreous UVAROVITE
(Garnet Group)
Ca₃Cr₂(SiO₄)₃ Isometric Usually as small to tiny dodecahedral crystals 3.40 to 3.83 Largely restricted to chrome-bearing deposits, particularly serpentinite ultramafics containing chromite. Rare. Goldmanite and knorringite are very rare dark-green and blue-green Garnet Group species, but are found in different mineral environments than uvarovite.

7 to7½ Pink to Red, Brownish-orange to Orange, Cinnamon, Yellow to Yellow-green, Pale-green to Grass-green to Emerald-green, Colorless Vitreous GROSSULAR
(Garnet Group)
Ca₃Al₂(SiO₄)₃ Isometric Usually as small dodecahedral crystals 3.42 to 3.80 Largely found in contact and regionally metamorphosed impure calcareous rocks, and in serpentinite and rodingite ultramafic rocks. Hibschite and katoite are very rare Garnet Group species that can be similar greens or milky to colorless, but they are found in different mineral environments than grossular.

7 to7½ Brown, Brownish-red to Brownish-yellow, Yellow to Yellow-green, Greyish-green to Medium- or Deep-green, Black Vitreous ANDRADITE
(Garnet Group)
Ca₃Fe₂(SiO₄)₃ Isometric Usually as small to medium sized dodecahedral crystals 3.45 Usually from Ca and Fe rich contact metamorphic rocks and skarns, also from alkaline and ultrabasic igneous rocks. Calderite is a very rare Garnet Group species with color similar to andradite, but it is found in a different mineral environment.

Hardness Color Luster Name System Habit SG Notes

7 to 7½ Black to Brownish-black Vitreous SCHORLOMITE
(Garnet Group)
Ca₃Ti₂(Fe₂Si)O₁₂ Isometric Usually as small dodecahedral crystals 3.77 to 3.93 Largely restricted to alkaline igneous rocks. Morimotoite and kimzeyite are very rare Garnet Group species that may be the same color as schorlomite, but they are found in different environments

7 to 7½ Dark-red to Violet-red or Deep rose-red, also Reddish-orange Vitreous PYROPE
(Garnet Group)
Mg₃Al₂(SiO₄)₃ Isometric Usually as small to tiny dodecahedral crystals 3.65 to 3.82 Usually found in high temperature and high pressure metamorphic rocks, ultrabasic igneous rocks, and kimberlites and peridotites. Uncommon. Majorite is a very rare Garnet Group species that can be purplish-violet, but is found in a different environment than pyrope.

7 to 7½ Brown to Brownish-red to Red, Violet-red or Orangish-red Vitreous ALMANDINE
(Garnet Group)
Fe₃Al₂(SiO₄)₃ Isometric Usually as dodecahedral crystals 3.85 to 4.20 Occurs in a number of metamorphic and igneous environments – most common of the Garnet Group species.

Hardness Color Luster Name System Habit SG Notes

7 to 7½ Orangish-red to Reddish-orange, Rose-red to Ruby-red or Hyacinth-red, Reddish-brown, Pale-yellow Vitreous SPESSARTINE
(Garnet Group)
Mn₃Al₂(SiO₄)₃ Isometric Usually as medium to tiny dodecahedral crystals 3.90 to 4.20 Occurs in metamorphic and igneous rocks rich in Mn.

7 to 7½ Medium- to Dark-brown, Reddish-brown Vitreous to sub-vitreous, may also be dull STAUROLITE
(Fe,Mg,Zn)₂Al₉(Si,Al)₄O₂₂(OH)₂ Monoclinic pseudo. Orthorhombic Usually as either short- to long-prismatic crystals, frequently twinned ("fairy crosses"), with twining at either 90^o or 60^o 3.74 to 3.83 Usually in intermediate grade pelitic metamorphic rocks

7 to 7½ Greyish-blue to Blue, Grey, Greenish-blue, Violet Vitreous to oily CORDIERITE
(Beryl Group?)
(Mg,Fe)₂Al₃[AlSi₅O₁₈] ^. H₂O Orthorhombic Usually granular or massively crystalline aggregates, crystals short-prismatic 2.53 to 2.65 Largely restricted to contact metamorphic rocks and high-grade regional metamorphic rocks.

7½ Reddish-brown to Pale-pink to Deep-pink/Flesh-colored, White to Grey to Bluish-grey to Blue, Olive-green, Green, Violet, Yellow Vitreous to sub-vitreous, may be dull ANDALUSITE
Al₂SiO₅ Orthorhombic Usually as prismatic crystals with a nearly square cross-section, may be tapered in both directions from the center and exhibit a cross-like pattern on the cross section due to carbonaceous inclusions ("chiastolite") 3.13 to 3.21 Largely a mineral of low to intermediate grade metamorphic rocks, but also known from granites and granite-pegmatites

Hardness Color Luster Name System Habit SG Notes

7½ Brown, White, Yellow, Orange, Green, Blue Adamantine, oily on fracture surfaces ZIRCON
ZrSiO₄ Tetragonal Usually as small tetragonal prisms with pyramidal terminations, may also be bipyramidal without the prism 4.6 to 4.71 Fluoresces orange-yellow, yellow and orange. This mineral may also be metamict (structurally disrupted by radiation) and then exhibits a lower H. (6 to 7) and S.G 3.9 to 4.6 range.

7½ to 8 Pale-blue to Pale-green (gem: "aquamarine")
Yellow to Golden-yellow (gem: "heliodore"),
Pink to light-red (gem: "morganite"),
White to Tan,
Emerald-green (gem: "emerald")
Colorless Vitreous BERYL
Be₃Al₂Si₆O₁₈ Hexagonal Usually as stout prismatic hexagonal crystals, also granular in matrix 2.63 to 2.78 Most often found in granite-pegmatites and rhyolites, but known from other environments as well.

Hardness Color Luster Name System Habit SG Notes

7½ to 8 White to Colorless Vitreous PHENAKITE
Be₂SiO₄ Trigonal Usually massive, granular, and as modified flattened rhombs, more rarely as prismatic crystals 2.97 to 3.0 Usually found with beryl in pegmatites.

7½ to 8 Dark-green to Greenish-black, more rarely Dark-yellow to Pale-yellow Vitreous to sub-vitreous, may be dull GAHNITE
(Spinel Group)
ZnAl₂O₄ Isometric Usually massive, granular, also as octahedral crystals, may be rounded or sharp 4.57 Usually in high-temperature ore deposits in crystalline schists or in pegmatites.

7½ to 8 Red, Black, Brown, Blue, Green Vitreous to sub-vitreous SPINEL
MgAl₂O₄ Isometric Usually massive, granular, and as octahedral crystals, often twinned 3.56 Distinguished from gahnite by it's lower specific gravity

8½ Yellow to Emerald-green Vitreous CHRYSOBERYL
BeAl₂O₄ Orthorhombic Usually as tabular or prismatic crystals, often twinned in heart or fish-tail shapes, may also be cyclically twinned in pseudo-hexagonal crystals 3.75 May appear red or brownish-pink in incandescent light ("alexandrite").

9 Dark-grey to Light-grey to Blue-grey to Blue (sapphire), Red (ruby), and Yellow, Brown and Green (sapphire) Vitreous to sub-vitreous and dull CORUNDUM
Al₂O₃ Trigonal Usually massive, granular (emery) and as barrel-shaped prismatic hexagonal crystals 4.0 Extremely hard – can only be scratched by moissanite (silicon carbide) and diamond.

Notes:
The Tourmaline Group species can be difficult to tell apart without specific locality data. The overlap of color and habit can make crystals without matrix very difficult to distinguish without lab tests.
Most of the Garnet Group species can be very difficult to tell apart. Color alone is rarely – if ever – diagnostic; and S.G.s overlap too much to make them useful alone or with color. Mineral environment information is usually needed in conjunction with S.G. and color to even begin to guess the species. The best bet is specific knowledge of what is found at any given locality – or lab tests in the absence of that. (Far too many "visual identifications" prove to be wrong…)
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Hardness	Color	Luster	Name	System	Habit	SG	Notes
6 to 7	Black to Dark-brown, may also be Yellowish-grey, more rarely Red, White or Colorless	Adamantine to metallic in crystals, greasy on fracture surfaces, may be earthy or submetallic in botryoids, concretions, and massive forms	CASSITERITE (Rutile Group) SnO₂	Tetragonal	Usually massive as botryoidal crusts or concretions ("wood tin"), crystals usually short prismatic and complexly twinned producing unusual shapes ("knees", stubby five-pointed "stars," etc.)	6.8 to 7.1
6½ to 7	Grey to Bluish-grey, Brown to Honey-brown or Yellow to Golden-brown, more rarely Green or Violet	Vitreous to sub-vitreous	FERRO-AXINITE/ MANGANAXINITE Ca₂FeAl₂BSi₄O₁₅(OH) Ca₂MnAl₂BSi₄O₁₅(OH)	Triclinic	Usually as thin wedge-shaped "axhead" crystals, often arranged in rosettes	3.23 to 3.32 (ferro-), 3.30 to 3.36 (mangan-)	End members difficult to distinguish, though low end and high end S.G. may do the trick. Magnesio-axinite and tinzenite are two rare related species.
6½ to 7	Pale-yellow to Olive-green to Olive-brown, Black	Vitreous to sub-vitreous (forsterite) or submetallic to dull (fayalite)	FAYALITE/ FORSTERITE (Olivine Group) Fe₂(SiO₄) Mg₂(SiO₄)	Orthorhombic	Usually as crystalline massive or granular, crystals short-prismatic	4.39 (fayalite) to 3.24 (forsterite)	End members distinguished by S.G. and luster. "Peridot" is the name for gem material in the fayalite-forsterite series, usually forsterite. Names for intermediate members of the series, such as "chrysolite" and "hortonolite" are based on chemical composition and should not be used unless the composition is known.
Hardness	Color	Luster	Name	System	Habit	SG	Notes
6½ to 7	Colorless to White, more rarely Pale-yellow, Pale-pink or Pale-brown	Vitreous	BERTRANDITE Be₄Si₂O₇(OH)₂	Orthorhombic	Usually as tiny to micro tabular crystals, also granular aggregates	2.57 to 2.63	Usually associated with beryl in pegmatites. May exhibit basal and prismatic cleavages.
7	Colorless, Milky, Smoky-grey to Black, Amethyst, Rose, Yellow to Brownish-yellow, may be tinted other shades by inclusions	Vitreous	QUARTZ (Crystalline) SiO₂	Trigonal	Usually in pyramidally terminated prismatic hexagonal crystals or glassy massive, "rock crystal," "smoky" and "amethyst" varieties may be very large, "citrine" usually small to medium in size, "rose" usually rather small to micro-scale	2.65	Abundant! in milky and massive forms. Common in rock crystal, smoky and amethyst forms, citrine rare, rose crystals very rare. (See also immediately below for crypto- and non-crystalline forms.)
Hardness	Color	Luster	Name	System	Habit	SG	Notes
7	Colorless, Milky, Grey to Black, Red, Yellow to Brownish-yellow, Brown, Green, Blue, may be tinted other shades by inclusions	Vitreous to waxy to dull	QUARTZ (Crypto- and Non-crystalline) SiO₂	Trigonal	"Chalcedony" as cryptocrystalline fibrous amorphous to sub-botryoidal masses, un-banded or un-patterned, with a waxy luster ("carnelian" is red, "chrysoprase" is green due to nickel, "heliotrope" or "bloodstone" is green with small red jasper flecks in it, "sard" is brown); "chalcedony, sub-variety agate" in circular, concentrically banded to intricately patterned masses with considerable color variation in single samples, waxy to vitreous luster; "chalcedony sub-variety onyx" has parallel layers instead of concentric ones ("sardonyx" has alternating white and black layers).	2.65	In massive, non- crystalline forms: "Jasper" red or blue, rarely yellow, dull luster; "flint" dark grey to black, dull to sub-vitreous luster; "chert" medium to light grey, dull to sub-vitreous luster; "aventurine" green due to inclusions, vitreous luster.
Hardness	Color	Luster	Name	System	Habit	SG	Notes
7	Colorless, Milky-white, Pale-grey, Yellowish, and Brownish	Vitreous	CRISTOBALITE SiO₂	Tetragonal (pseudo Isometric)	Usually as micro-spherical aggregates, may be botryoidal or stalactic, crystals very rare, usually micro-octahedra	2.2 to 2.33	Largely restricted to siliceous volcanic rocks. Cristobalite is only partially stable at typical terrestrial temperatures, inverting to quartz. Most finds are actually quartz pseudomorphs of the original crystals
7	Colorless, Milky-white	Vitreous	TRIDYMITE SiO₂	Orthorhombic & Hexagonal	Usually as thin to thick tabular or twinned pseudo-hexagonal crystals	2.26 to 2.33	Largely restricted to felsic volcanic rocks; Tridymite is only partially stable at typical terrestrial temperatures, inverting to quartz. Most finds are actually quartz pseudomorphs of the original crystals
7 to 7½	Black to Bluish-black or Brownish-black or Greenish-black	Vitreous to sub-vitreous, may appear somewhat oily on fracture surfaces	SCHORL / UVITE (Tourmaline Group) NaFe₃Al₆ (BO₃)₃(Si₆O₁₈)(OH)₄ (Ca,Na)(Mg,Fe)₃Al₅Mg(BO₃)₃(Si₆O₁₈)(OH,F)₄	Trigonal	Schorl usually in stout to long-prismatic six-sided crystals with a nearly triangular cross-section. Uvite usually in stubby short-prismatic crystals, sometimes appearing almost pyramidal or dipyramidal, but may take identical habits. Both may also be massively crystalline or granular.	3.13 (schorl) 2.96 to 3.06 (uvite)	These two end members are best distinguished by their S.G.s. Foitite, feruvite, and povondrite are three rare to very rare black Tourmaline Group members.
Hardness	Color	Luster	Name	System	Habit	SG	Notes
7 to 7½	Black to Brownish-black or Brown	Vitreous to sub-vitreous, may appear oily on fracture surfaces	DRAVITE (Tourmaline Group) NaMg₃Al₆(BO₃)₃(Si₆O₁₈)(OH)₄	Trigonal	Usually as stout prismatic six-sided crystals, often with a pyramidal termination at one end and a pedial termination at the other	2.9 to 3.3	Largely restricted to marbles, schists and slates. Best distinguished from schorl and uvite by environment when black. Buergerite is a rare bronze-brown Tourmaline Group member.
7 to 7½	Dark emerald-green to Greenish-black to Black	Vitreous, may appear oily on fracture surfaces	CHROMEDRAVITE (Tourmaline Group) NaMg₃(Cr,Fe)₆ (BO₃)₃ (Si₆O₁₈)(OH)₄	Trigonal	Usually as small to tiny nearly equant short-prismatic crystals and grains	3.39 to 3.40	Usually distinguished by its deep emerald green color – largely restricted to chromium bearing micaceous metasomatites. Very rare. Distinguished from dark greenish-black schorl or uvite by its higher S.G
7 to 7½	Light- to Medium-green, Pink to Red, Light- to Medium-blue to Dark-blue, more rarely Light-brown to Yellow, Colorless	Vitreous to oily	ELBAITE (Tourmaline Group) Na(Li,Al)₃Al₆ (BO₃)₃(Si₆O₁₈)(OH)₄	Trigonal	Usually in slender prismatic six-sided crystals with a nearly triangular cross-section, often appearing somewhat rounded. Whole crystals may be hemimorphic, with different shaped terminations (pyramidal and pedial) at opposite ends	3.05 to 3.10	Distinguished from most other Tourmaline Group species by its lighter colors – also, largely restricted to granite-pegmatites. Dark-blue elbaite is almost impossible to distinguish from dark blue schorl, and both can occur together. Olenite, pale pink, and liddicoatite, light-pink or light-green, are two rare to very rare colored Tourmaline Group species.
Hardness	Color	Luster	Name	System	Habit	SG	Notes
7 to7½	Deep-green to "Rusty"-green	Vitreous	UVAROVITE (Garnet Group) Ca₃Cr₂(SiO₄)₃	Isometric	Usually as small to tiny dodecahedral crystals	3.40 to 3.83	Largely restricted to chrome-bearing deposits, particularly serpentinite ultramafics containing chromite. Rare. Goldmanite and knorringite are very rare dark-green and blue-green Garnet Group species, but are found in different mineral environments than uvarovite.
7 to7½	Pink to Red, Brownish-orange to Orange, Cinnamon, Yellow to Yellow-green, Pale-green to Grass-green to Emerald-green, Colorless	Vitreous	GROSSULAR (Garnet Group) Ca₃Al₂(SiO₄)₃	Isometric	Usually as small dodecahedral crystals	3.42 to 3.80	Largely found in contact and regionally metamorphosed impure calcareous rocks, and in serpentinite and rodingite ultramafic rocks. Hibschite and katoite are very rare Garnet Group species that can be similar greens or milky to colorless, but they are found in different mineral environments than grossular.
7 to7½	Brown, Brownish-red to Brownish-yellow, Yellow to Yellow-green, Greyish-green to Medium- or Deep-green, Black	Vitreous	ANDRADITE (Garnet Group) Ca₃Fe₂(SiO₄)₃	Isometric	Usually as small to medium sized dodecahedral crystals	3.45	Usually from Ca and Fe rich contact metamorphic rocks and skarns, also from alkaline and ultrabasic igneous rocks. Calderite is a very rare Garnet Group species with color similar to andradite, but it is found in a different mineral environment.
Hardness	Color	Luster	Name	System	Habit	SG	Notes
7 to 7½	Black to Brownish-black	Vitreous	SCHORLOMITE (Garnet Group) Ca₃Ti₂(Fe₂Si)O₁₂	Isometric	Usually as small dodecahedral crystals	3.77 to 3.93	Largely restricted to alkaline igneous rocks. Morimotoite and kimzeyite are very rare Garnet Group species that may be the same color as schorlomite, but they are found in different environments
7 to 7½	Dark-red to Violet-red or Deep rose-red, also Reddish-orange	Vitreous	PYROPE (Garnet Group) Mg₃Al₂(SiO₄)₃	Isometric	Usually as small to tiny dodecahedral crystals	3.65 to 3.82	Usually found in high temperature and high pressure metamorphic rocks, ultrabasic igneous rocks, and kimberlites and peridotites. Uncommon. Majorite is a very rare Garnet Group species that can be purplish-violet, but is found in a different environment than pyrope.
7 to 7½	Brown to Brownish-red to Red, Violet-red or Orangish-red	Vitreous	ALMANDINE (Garnet Group) Fe₃Al₂(SiO₄)₃	Isometric	Usually as dodecahedral crystals	3.85 to 4.20	Occurs in a number of metamorphic and igneous environments – most common of the Garnet Group species.
Hardness	Color	Luster	Name	System	Habit	SG	Notes
7 to 7½	Orangish-red to Reddish-orange, Rose-red to Ruby-red or Hyacinth-red, Reddish-brown, Pale-yellow	Vitreous	SPESSARTINE (Garnet Group) Mn₃Al₂(SiO₄)₃	Isometric	Usually as medium to tiny dodecahedral crystals	3.90 to 4.20	Occurs in metamorphic and igneous rocks rich in Mn.
7 to 7½	Medium- to Dark-brown, Reddish-brown	Vitreous to sub-vitreous, may also be dull	STAUROLITE (Fe,Mg,Zn)₂Al₉(Si,Al)₄O₂₂(OH)₂	Monoclinic pseudo. Orthorhombic	Usually as either short- to long-prismatic crystals, frequently twinned ("fairy crosses"), with twining at either 90^o or 60^o	3.74 to 3.83	Usually in intermediate grade pelitic metamorphic rocks
7 to 7½	Greyish-blue to Blue, Grey, Greenish-blue, Violet	Vitreous to oily	CORDIERITE (Beryl Group?) (Mg,Fe)₂Al₃[AlSi₅O₁₈] ^. H₂O	Orthorhombic	Usually granular or massively crystalline aggregates, crystals short-prismatic	2.53 to 2.65	Largely restricted to contact metamorphic rocks and high-grade regional metamorphic rocks.
7½	Reddish-brown to Pale-pink to Deep-pink/Flesh-colored, White to Grey to Bluish-grey to Blue, Olive-green, Green, Violet, Yellow	Vitreous to sub-vitreous, may be dull	ANDALUSITE Al₂SiO₅	Orthorhombic	Usually as prismatic crystals with a nearly square cross-section, may be tapered in both directions from the center and exhibit a cross-like pattern on the cross section due to carbonaceous inclusions ("chiastolite")	3.13 to 3.21	Largely a mineral of low to intermediate grade metamorphic rocks, but also known from granites and granite-pegmatites
Hardness	Color	Luster	Name	System	Habit	SG	Notes
7½	Brown, White, Yellow, Orange, Green, Blue	Adamantine, oily on fracture surfaces	ZIRCON ZrSiO₄	Tetragonal	Usually as small tetragonal prisms with pyramidal terminations, may also be bipyramidal without the prism	4.6 to 4.71	Fluoresces orange-yellow, yellow and orange. This mineral may also be metamict (structurally disrupted by radiation) and then exhibits a lower H. (6 to 7) and S.G 3.9 to 4.6 range.
7½ to 8	Pale-blue to Pale-green (gem: "aquamarine") Yellow to Golden-yellow (gem: "heliodore"), Pink to light-red (gem: "morganite"), White to Tan, Emerald-green (gem: "emerald") Colorless	Vitreous	BERYL Be₃Al₂Si₆O₁₈	Hexagonal	Usually as stout prismatic hexagonal crystals, also granular in matrix	2.63 to 2.78	Most often found in granite-pegmatites and rhyolites, but known from other environments as well.
Hardness	Color	Luster	Name	System	Habit	SG	Notes
7½ to 8	White to Colorless	Vitreous	PHENAKITE Be₂SiO₄	Trigonal	Usually massive, granular, and as modified flattened rhombs, more rarely as prismatic crystals	2.97 to 3.0	Usually found with beryl in pegmatites.
7½ to 8	Dark-green to Greenish-black, more rarely Dark-yellow to Pale-yellow	Vitreous to sub-vitreous, may be dull	GAHNITE (Spinel Group) ZnAl₂O₄	Isometric	Usually massive, granular, also as octahedral crystals, may be rounded or sharp	4.57	Usually in high-temperature ore deposits in crystalline schists or in pegmatites.
7½ to 8	Red, Black, Brown, Blue, Green	Vitreous to sub-vitreous	SPINEL MgAl₂O₄	Isometric	Usually massive, granular, and as octahedral crystals, often twinned	3.56	Distinguished from gahnite by it's lower specific gravity
8½	Yellow to Emerald-green	Vitreous	CHRYSOBERYL BeAl₂O₄	Orthorhombic	Usually as tabular or prismatic crystals, often twinned in heart or fish-tail shapes, may also be cyclically twinned in pseudo-hexagonal crystals	3.75	May appear red or brownish-pink in incandescent light ("alexandrite").
9	Dark-grey to Light-grey to Blue-grey to Blue (sapphire), Red (ruby), and Yellow, Brown and Green (sapphire)	Vitreous to sub-vitreous and dull	CORUNDUM Al₂O₃	Trigonal	Usually massive, granular (emery) and as barrel-shaped prismatic hexagonal crystals	4.0	Extremely hard – can only be scratched by moissanite (silicon carbide) and diamond.