The Mineral Identification Key

Table IID-1: Nonmetallic Luster, Hardness Greater Than 3 but Less Than 5½, and Prominent Cleavage: (Can not be scratched by a copper penny, can be scratched by a knife, streak white or none.) [Previous Table]  [Next Table] 

Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Imperfect in one direction (basal), may be distinct in another direction (rhombic) but usually not seen	3 to 3½	Colorless to White or Greyish-white, may be tinted other colors	Vitreous to sub-vitreous	WITHERITE (Aragonite Group) BaCO3	Orthorhombic, pseudo- hexagonal	Usually as stout prismatic twinned crystals with a hexagonal cross section, often with pyramidal terminations on both ends, more rarely as globular to botryoidal clusters, coarse fibrous aggregates, and granular	4.29	Often hazed, will effervesce in cold acid.
Distinct in one direction	3½ to 4	Colorless to White or Grey, may be tinted other colors	Vitreous to sub-vitreous or resinous	ARAGONITE (Aragonite Group) CaCO3	Orthorhombic	Usually in prismatic crystals, sometimes flattened, often acicular, usually twinned producing a pseudo-hexagonal cross section, may also be columnar, radiating or stellate aggregates, also stalactic	2.95	Often fluorescent, pale rose, yellow or bluish-white, effervesces in cold acids. Distinguished from calcite by its greater hardness, higher S.G. and different crystal forms and habits – though some crystals may mimic the forms found in calcite.
Cleavage	Hardness	Color	Luster	Name	System	Habit	Sp. G	Notes
Perfect cleavage in one direction	3½ to 4	Colorless to White, may be Yellow, Brown, and other colors	Vitreous, pearly on cleavage surfaces	STILBITE-(Ca) (Zeolite Group) (Ca0.5,Na,K)9[Al9Si27O72].28H2O	Monoclinic	Usually as flattened tabular long prismatic crystals, often in sheaf-like groups ("bowties")	2.12 to 2.22	White streak; dissolves in cold acids.
Perfect cleavage in one direction	3½ to 4	Colorless to White, may be Grey, Yellow, Pink, and other colors	Vitreous, pearly on cleavage surfaces	HEULANDITE-(Ca) (Zeolite Group) (Ca0.5,Na,K)9[Al9Si27O72].~24H2O	Monoclinic	Commonly tabular to equant crystals, may be long-prismatic, typically coffin shaped	2.10 to 2.29	White streak; dissolves in cold acids.
Perfect cleavage in one direction	3½ to 4	Colorless to White	Vitreous, pearly on cleavage surfaces	CLINOPTILOLTE-(Ca) (Zeolite Group) (Ca0.5,Na,K)6[Al6Si30O72].~20H2O	Monoclinic	Usually as platy crystals, may be tabular or flattened long prismatic, commonly fine-grained, massive	2.10 to 2.17	White streak; dissolves in cold acids.
Perfect cleavage in one direction	4½	Colorless to White, may be Pink or Brown	Vitreous to sub-vitreous	STELLERITE (Zeolite Group) Ca[Al2Si7O18].7H2O	Orthorhombic	Usually in spheres of radiating elongated tabular crystals, often also as aggregates of scaly to platy and small tabular crystals	2.13	White streak; dissolves in cold acids.
Perfect in one direction, may have a poor (pinacoidal) cleavage in another direction	4½ to 5½	Colorless to White, Pale-pink, Pale-yellow to Pale-brown	Vitreous, pearly on some cleavage surfaces	BREWSTERITE-Sr/ BREWSTERITE-Ba (Sr,Ba)2[Al4Si12O32].10H2O (Ba,Sr)2[Al4Si12O32].10H2O	Monoclinic & Triclinic	Usually as small tabular crystals, may be blocky or prismatic as well	2.32 to 2.45	White streak; S.G. increases with Ba content; Brewsterite-Ba is the far more common of the two.
Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Perfect  in one direction (prismatic)	5 to 5½	Colorless to White, Pale-pink, may be Grey or other colors	Usually vitreous to silky in finer acicular aggregates, but may be dull or even greasy	NATROLITE (Zeolite Group) Na2[Al2Si3O10].2H2O	Orthorhombic	Usually as long slender needles in stellate clusters or radial aggregates, may also be in jackstraw clusters	2.20 to 2.27	White streak; partially decomposed by acid, producing a white gel.
Poor in one direction, may not be seen	5 to 5½	Colorless to White, may be Yellow, Pink, or other colors	Vitreous	ANALCIME (Zeolite Group) Na[AlSi2O6].H2O	Polymorphous (Iso., Tet., Orth., Mon., Tric., Trig.)	Usually in cubic or trapezohedral crystals or fine-grained masses, more rarely in other crystal forms	2.22 to 2.63	Dissolves in cold acids
Perfect in one direction (may have a distinct cleavage in a second direction)	4 to 4½	Colorless to White or Grey, may be tinted other colors	Vitreous to sub-adamantine	COLEMANITE Ca2B6O11.5H2O	Monoclinic	Usually  druzy, massive granular, equant to short prismatic crystals	2.42	Decrepitates violently in a candle flame.
Perfect in one direction (may have an imperfect cleavage in a second direction)	4½ to 5	Colorless to White or Grey, Pale-green, may also be other tints	Vitreous to sub-vitreous, pearly on cleavage surfaces	FLUORAPOPHYLLITE/ HYDROXYLAPOPHYLLITE KCa4Si8O20F.8H2O    KCa4Si8O20(OH).8H2O	Tetragonal	Crystals usually equant, blocky, may be stout tabular, more rarely prismatic, commonly striated	2.33 to 2.37	It is impossible to tell the two end members apart without subtle chemical tests.  Information about which is found at any given locality is the best bet.  Fluorapophyllite is probably the more common of the two.
Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Perfect in one direction (may have a good cleavage in another direction)	4½  to 5 parallel to the length of the crystal, 7 to 7½ across the crystal	Blue most common, also Green, may be Grey, even Black, due to inclusions	Vitreous to subvitreous	KYANITE Al2SiO5	Triclinic	Most often as bladed long-prismatic crystals, usually poorly formed and rarely terminated, may be in parallel groupings or randomly oriented in the matrix	3.56 to 3.76	Only common mineral with significant hardness difference in two directions.
Two  directions: Perfect in one direction (prismatic), poor in another direction (prismatic)	3½ to 4	Colorless to White or Grey, may be tinted other colors	Vitreous to sub-vitreous, silky when fibrous	STRONTIANITE (Aragonite Group) SrCO3	Orthorhombic	Usually in granular or fibrous aggregates, may be columnar, crystals short prismatic to acicular, often pseudo-hexagonal in cross-section (Ca-rich)	3.76	Effervesces mildly in cold acids, or not at all.  Distinguished from cerussite by its notably lower specific gravity, lighter feel.  Also it is not as common as cerussite.
Two directions: Perfect in one direction, imperfect in a second	4½	Bluish-grey to Greenish-Grey (triphylite), White to Greyish-white streak, Clove-brown to Yellowish-brown, Salmon (lithiophilite)	Vitreous to sub-vitreous, may be dull in granular massive material	TRIPHYLITE/ LITHIOPHILITE LiFePO4   LiMnPO4	Orthorhombic	Usually in cleavable crystalline masses, crystals rare and usually crude with uneven surfaces, stout prismatic	3.56 (triphylite), 3.34 (lithiophilite)
Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Two directions: Perfect in one direction (prismatic), poor in a second direction (cleavages rarely seen)	4½ to 5	Colorless to White, may be Pale-yellow, Pale-green, Sky-blue, Pale-brown	Vitreous, pearly on some cleavage surfaces	HEMIMORPHITE Zn4Si2O7(OH)2.H2O	Orthorhombic	Usually in radiating clusters of acicular or somewhat flattened long prismatic crystals, may also be in thick botryoidal crusts of thick to almost fibrous radiating crystals	3.4 to 3.5	May resemble prehnite in its botryoidal form, but S.G. is higher
Two directions: Perfect in both directions (pinacoidal)	4½ to 5	White, Pale-pink, Pale-tan, Pale-blue	Vitreous to silky in fibrous material	PECTOLITE (Wollastonite Group) NaCa2Si3O8(OH)	Triclinic	Usually in acicular sprays or radial fibrous aggregates	2.84 to 2.90	Partly decomposed in acid forming a gel
Two directions: Perfect in one direction (pinacoidal), good in a second (pinacoidal), may exhibit a poor to good third cleavage (rarely seen)	4½ to 5	White to Greyish-white, may also be Pale-green	Vitreous to somewhat pearly in fibrous material	WOLLASTONITE-1A (Wollastonite Group) CaSiO3	Triclinic	Usually in coarsely crystalline cleavage masses, more rarely fibrous	2.86 to 3.09	Most common of the wollastonite polymorphs. Found in contact metamorphism of siliceous limestones
Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Two directions: Perfect in two directions (both pinacoidal)	4½ to 5	Orange to Pinkish-orange to Rose	Vitreous, pearly on cleavage surfaces	SERANDITE (Wollastonite Group) Na(Mn,Ca)2Si3O8(OH)	Triclinic	Usually as slightly flattened prismatic crystals in parallel to sub-parallel groups	3.0 to 3.4	Rare
Two directions: Perfect in one direction, imperfect parting in a second direction (both prismatic)	5 to 5½	Yellowish-brown to Greenish-brown	Vitreous to sub-vitreous, may be somewhat resinous or oily	TITANITE  ("SPHENE") CaTiSiO5	Monoclinic	Usually in crude blocky to stout prismatic crystals, wedge-shaped	3.48 to 3.60	Streak white to pale brown
Two directions: Perfect in both directions at nearly 90o to one another (prismatic)	5½ to 6½	Pink to Rose-red, Brownish-red, usually coated with black manganese oxides	Vitreous to sub-vitreous, may be somewhat pearly on cleavage surfaces	RHODONITE (Mn,Fe,Mg,Ca)SiO3	Triclinic	Usually massive, granular, rarely as tabular crystals	3.55 to 3.76
Two directions: Perfect in two directions	5½ to 6	Dark Greenish-black to Black	Vitreous, splendant.	BABINGTONITE Ca2(Fe,Mn)FeSi5O14(OH)	Triclinic	Usually as equant to stout prismatic to tabular crystals, often crude	3.34 to 3.48	Pale greenish to brownish grey streak
Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Two directions: Perfect in both directions (both pinacoidal)	4 to 4½	Colorless to White, may be Pink to Orange-red	Silky to vitreous	DACHIARDITE-Ca (Zeolite Group) (Ca0.5,K,Na)4-5[Al4-5Si20-19O48] .~13H2O	Monoclinic	Usually fibrous to small bladed prismatic crystals in radiating aggregates or clusters	2.14 to 2.21	White streak; Rare.
Two directions: Distinct in one direction, indistinct in another (both pinacoidal)	4 to 4½	Colorless to White, may be Pink to Red, Yellow	Vitreous	PHILLIPSITE-Ca (Zeolite Group) (Ca0.5,K,Na,Ba0.5)4-7[Al4-7,Si12-9O32]·12H2O	Monoclinic	Usually as small twinned, pseudo-orthorhombic, prismatic crystals	2.2	White streak; Forms a series with harmotome.
Two directions: Good in one direction, fair in another (both pinacoidal), fair cleavage may not be seen	4½ to 5	Colorless to White or Greyish-white, may be tinted other colors	Vitreous	HARMOTOME (Zeolite Group) (Ba0.5,Ca0.5,K,Na)5[Al5Si11O32]·12H2O	Monoclinic	Usually as blocky crystals, but may be twinned, pseudo-orthorhombic, prismatic crystals	2.38 to 2.50 (increasing with Ba content)	Streak white; Forms a series with phillipsite
Two directions: Perfect in one direction, poor in another, (pinacoidal), second may not be seen	4½ to 5½	Colorless to White, Pale-pink, Pale-yellow to Pale-brown	Vitreous, pearly on some cleavage surfaces	BREWSTERITE-Sr/ BREWSTERITE-Ba (Sr,Ba)2[Al4Si12O32].10H2O (Ba,Sr)2[Al4Si12O32].10H2O	Monoclinic & Triclinic	Usually as small tabular crystals, may be blocky or prismatic as well	2.32 to 2.45 (increasing with Ba content)	Brewsterite-Ba is the far more common of the two
Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Two directions: Perfect in both directions (both prismatic)	5	Colorless to White, may be Pink to Red, Yellowish or Green	Silky when fibrous, vitreous when acicular	MESOLITE (Zeolite Group) Na16Ca16[Al48Si72O240].64H2O	Orthorhombic	Usually in fibrous radiating aggregates or long slender needles in sprays, stellate clusters, or jackstraw clusters, may also be fibrous tufts	2.25	White streak;
Two directions: Perfect in both directions (both prismatic)	5 to 5½	Colorless to White, Pink to Red or Salmon, Green	Vitreous, silky in fibrous material	SCOLECITE (Zeolite Group) Ca[Al2Si3O10].3 H2O	Monoclinic	Usually as thin flattened prismatic needles in stellate to radiating clusters, may also be in fibrous radiating aggregates	2.24 to 2.31	Rare.
Two directions: Perfect in one direction (prismatic), good to distinct in a second direction (actually a parting, but distinct – prismatic)	5 to 5½	Colorless to White, Pale-pink to Pale-red, may be other colors	Vitreous, silky in more fibrous aggregates, more rarely greasy or dull	NATROLITE (Zeolite Group) Na2[Al2Si3O10].2H2O	Orthorhombic	Usually as long slender needles or prismatic crystals (nearly square cross-section, pseudo-tetragonal) in radial aggregates or stellate or jackstraw clusters	2.20 to 2.27	White streak; partially decomposed by acid, producing a white gel.
Two directions: Perfect in one direction, good in another (both pinacoidal), may not be seen	5 to 5½	Colorless to White, may be tinted other colors, white streak	Vitreous to pearly	THOMSONITE (Zeolite Group) Ca2Na[Al5Si5O20]. 6H2O	Orthorhombic	Usually in granular masses, crystals vary from thin rectangular blades to blocky prismatic	2.25 to 2.44	Partially decomposed by acid, producing a white gel.
Two directions at ~56o and ~124o : prismatic – Amphibole Group; Good to perfect in both directions	5 to 6	Grey to Lavender-blue or Pale-blue	Vitreous, silky in asbestiform varieties	GLAUCOPHANE/  FERROGLAUCOPHANE Na2(Mg3Al2)Si8O22(OH)2   Na2(Fe3Al2) Si8O22(OH)2	Monoclinic	Usually in lath-like crystal aggregates, striated along their length, and in fibrous ("asbestiform") aggregates ("crocidolite")	3.02 to 3.42 (increasing with Fe content)	Pale-grey to bluish-grey streak;  glaucophane usually light-grey to lavender-blue; ferroglaucophane usually darker. The glaucophanes and riebeckites are impossible to tell apart without subtle chemical or optical tests.
Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Two directions at ~56o and ~124o : prismatic – Amphibole Group; Good to perfect in both directions	5 to 6	Light-blue to Blue-black	Vitreous, silky in asbestiform varieties	MAGNESIORIEBECKITE/ RIEBECKITE Na2(Mg3Fe2)Si8O22(OH)2 Na2(Fe3Fe2)Si8O22(OH)2	Monoclinic	Usually in lath-like crystal aggregates, striated along their length, and in fibrous ("asbestiform") aggregates ("crocidolite")	3.02 to 3.42 (increasing with Fe content)	Pale-grey to bluish-grey streak; magnesioriebeckite usually lighter blue, riebeckite usually darker; glaucophanes and riebeckites are impossible to tell apart without subtle chemical or optical tests.
Two directions at ~56o and ~124o : prismatic – Amphibole Group; Perfect in both directions	5 to 6	White to Light-Green to Dark-green	Vitreous, silky in asbestiform varieties	TREMOLITE/ ACTINOLITE Ca2Mg5Si8O22(OH)2   Ca2(Fe,Mg)5Si8O22(OH)2	Monoclinic	Usually in bladed crystal aggregates, may also be somewhat acicular, tremolite may be asbestiform ("byssolite") or in fibrous mats ("mountain leather", "mountain cork"). The massive fibrous aggregate form of either is known as the variety nephrite, and is one of the materials called 'Jade.'	2.89 to 3.44 (increasing with Fe content)	Tremolite usually white to greyish-white or pale greenish-white, actinolite medium- to dark-green.
Two directions at ~56o and ~124o : prismatic – Amphibole Group; Good to perfect in both directions	5 to 6	Brown to Greenish-brown to Green or Greyish-green	Vitreous, silky in fibrous varieties	CUMMINGTONITE/ GRÜNERITE Mg7Si8O22(OH)2 Fe7Si8O22(OH)2	Monoclinic	Usually in bladed crystal aggregates or asbestiform, may be acicular	3.1 to 3.6 (increasing with Fe content)	Cummingtonite usually green to grey-green, grünerite brown to greenish-brown.
Cleavage	Habit	Color	Luster	Name	System	Habit	SG	Notes
Two directions at ~56o and ~124o : prismatic – Amphibole Group; Perfect in one direction, imperfect in the second	5½ to 6	White to Grey or Pale-green to Clove-brown or Dark-brown	Vitreous, silky in asbestiform varieties	ANTHOPHYLLITE/ FERROANTHOPHYLLITE Mg7Si8O22(OH)2    Fe7Si8O22(OH)2	Orthorhombic	Usually columnar aggregates, may be radiating, or asbestiform	3.18 to 3.57 (increasing with Fe content)	Anthophyllite usually lighter colors, ferroanthophyllite darker.
Two directions at ~56o and ~124o : prismatic – Amphibole Group; Perfect in one direction, imperfect in the other	5½ to 6	Pale Greenish-grey to Greenish-brown and Brown	Vitreous, silky when fibrous	GEDRITE/ FERROGEDRITE Mg5Al2[Si6Al2O22](OH)2   Fe5Al2[Si6Al2O22] (OH)2	Orthorhombic	Usually in lamellar to fibrous aggregates	3.18 to 3.57 (increasing with Fe content)	Gedrite usually paler shades, ferrogedrite darker.
Two directions at ~56o and ~124o : prismatic – Amphibole Group; Perfect in both directions	5 to 6	Black to Greenish-black or Dark-green	Vitreous	MAGNESIOHORNBLENDE/ FERROHORNBLENDE Ca2[Mg4(Al,Fe)]Si7AlO22(OH)2   Ca2[Fe4(Al,Fe)]Si7AlO22(OH)2	Monoclinic	Usually in coarsely crystalline cleavable masses, also in prismatic to acicular crystal aggregates with the crystals often displaying a crudely pseudo-hexagonal cross section, otherwise rectangular to nearly square, not asbestiform	3.02 to 3.45 (increasing with Fe content)	May give grey-green streak;  magnesiohornblende usually paler than ferrohornblende
Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Two directions at ~56o and ~124o : prismatic – Amphibole Group; Perfect in both directions	5 to 6	Pale-green to Dark-green, Greyish-brown to Brown, Yellow-brown to Reddish-brown or Rose-red	Vitreous, silky in asbestiform varieties	RICHTERITE/ FERRORICHTERITE Na(Ca,Na)Mg5Si8O22(OH)2 Na(Ca,Na)Fe5Si8O22(OH)2	Monoclinic	Usually in cleavable prismatic crystal aggregates or stout flattened prismatic crystals, also asbestiform	2.97 to 3.45 (increasing with Fe content)	Color darkens with increasing Fe content (ie: ferrorichterite).
Two directions at nearly 90o: prismatic – Pyroxene Group; Good to perfect in both directions	5 to 6	Pale to Medium-green, Pale-yellow to Light Yellowish-brown, Pale-bronze ("bronzite")	Vitreous to sub-vitreous, may be sub-metallic in the "bronzite" and "hypersthene" varieties	ENSTATITE/ CLINOENSTATITE Mg2Si2O6	Orthorhombic & Monoclinic	Usually granular in rocks, rarely as short-prismatic crystals	3.21 to 3.60	Enstatite-ferrosilite and clinoenstatite-clinoferrosilite form solid solution series.  They are very difficult to tell apart.  "Bronzite" and "hypersthene" are varietal names for intermediate members of the series.
Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Two directions at nearly 90o: prismatic – Pyroxene Group; Good in both directions	5 to 6	Greenish-brown or Brown to nearly Black	Vitreous to sub-vitreous, may be dull, may be pearly to sub-metallic on cleavage surfaces	FERROSILITE/ CLINOFERROSILITE (Fe,Mg)2Si2O6	Orthorhombic & Monoclinic	Usually granular in rocks, prismatic crystals rare	3.6 to 4.0	Streak pale grey to pale brown; Enstatite-ferrosilite and clinoenstatite - clinoferrosilite form solid solution series.  They are very difficult to tell apart.  "Bronzite" and "hypersthene" are varietal names for intermediate members of the series.
Two directions at nearly 90o: prismatic – Pyroxene Group; Good to perfect in both directions	5½ to 6	Pale- to Dark-green, may be White or Greenish-white to Greyish-white	Vitreous to sub-vitreous, may be dull	DIOPSIDE CaMgSi2O6	Monoclinic	Usually as equant to stout prismatic crystals, slender prismatic less common, more rarely tabular, also massive and granular	3.22 to 3.45	White to pale-green streak; may exhibit chatoyancy and 4-ray asterism when cut and polished with the correct orientation. Diopside and hedenbergite form a solid solution series.  They can be impossible to distinguish visually.  S.G. usually tells them apart, though when of intermediate composition this may not do the trick.
Two directions at nearly 90o: prismatic – Pyroxene Group; Good in both directions	5½ to 6	Pale- to Dark-green, Brownish-green to Brownish- or Greenish-black	Vitreous to sub-vitreous, may be dull	HEDENBERGITE CaFe Si2O6	Monoclinic	Usually as massive, granular, and as fracture fillings in rock, crystals equant to stout prismatic, slender prismatic less common, more rarely tabular	3.45 to 3.56	Pale green to tan streak;  may exhibit chatoyancy and 4-ray asterism when cut and polished with the correct orientation. Diopside and hedenbergite form a solid solution series.  They can be impossible to distinguish visually.  S.G. usually tells them apart, though when of intermediate composition this may not do the trick.
Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Two directions at nearly 90o: prismatic – Pyroxene Group; Good in both directions	5½ to 6	Greenish-black to Black, Light- to Dark-brown	Vitreous to sub-vitreous, may be dull	AUGITE (Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6	Monoclinic	Usually granular in rocks, also as somewhat flattened short-prismatic crystals	3.19 to 3.56	Pale brown to greenish grey streak
Two directions at nearly 90o: prismatic – Pyroxene Group; Good to perfect in both directions	5½ to 6	Dark-green or Reddish-brown to Black	Vitreous to sub-vitreous, may be dull	AEGIRINE (ACMITE) NaFeSi2O6	Monoclinic	Usually as slender prismatic or acicular crystals, either in clusters in cavities or as acicular aggregates in matrix	3.50 to 3.60	Pale tan to yellow green to pale green streak
Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Three directions: rhombohedral – Trigonal Carbonates: Perfect in all three directions	3, may be 2 across the top surface of prismatic crystals with a flat termination	Usually Clear or White to Tan or Grey, but may be tinted many colors	Vitreous to sub-vitreous luster, may be waxy or dull on weathered crystals, pearly on cleavage surfaces	CALCITE CaCO3	Trigonal	May be in cleavable masses producing rhombs, granular masses (limestone and marble), scalenohedral ("dogtooth") crystals, rhombohedral crystals, flattened rhombohedral ("nailhead") crystals, or a wide variety of related shapes (there are over 800 crystals forms known for this species to date…)	2.71	Clear rhombs show a doubled image of print viewed through them, , effervesces in cold, dilute acid – even in vinegar or Coke to a small degree. The many varied habits of calcite crystals make this one of the species that can be tough to identify by crystal form alone.  Few people, if any, are familiar with all the forms it takes.
Three directions: rhombohedral – Trigonal Carbonates: Perfect in all three directions	3½ to 4½	White to Grey, may be tinted Yellowish to Brownish	Vitreous to sub-vitreous, may be pearly on cleavage surfaces	MAGNESITE (Calcite Group) MgCO3	Trigonal	Usually massive, granular, crystals may be rhombohedral or prismatic but are rare	3.0	White streak;  only slightly soluble in cold acids.  No where near as common as calcite or dolomite.
Three  directions: rhombohedral – Trigonal Carbonates: Perfect in all three directions	3½ to 4	White to Tan or Pink, Grey, Greenish, tends towards Brown with increasing Fe, Red with Mn	Usually vitreous to sub-vitreous, but may be pearly	DOLOMITE CaMg(CO3)2	Trigonal	Usually as massive, granular, or in curved rhombohedral crystal clusters "fingernail" shape, druzes may have a characteristic "saddleback" arrangement	2.85	Streak same color as sample, but pale; powder effervesces in cold acid, though not as vigorously as calcite, may be fluorescent. The Dolomite Group minerals are best told apart – and from calcite – by their S.G. when color and habit coincides.
Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Three  directions: rhombohedral – Trigonal Carbonates:  Perfect in all three directions	3½ to 4	White to Tan or Brown	Usually vitreous to subvitreous, but may be pearly	ANKERITE (Dolomite Group) Ca(Fe,Mg,Mn)(CO3)2	Trigonal	Usually  massive, granular, or as rhombohedral crystals (similar to dolomite)	2.87	White streak;  powder effervesces in cold acids, though not as vigorously as calcite.  Not as common as either calcite or dolomite. The Dolomite Group minerals are best told apart – and from calcite – by their S.G. when color and habit coincides.
Three  directions: rhombohedral – Trigonal Carbonates: Perfect in all three directions	3½ to 4	White to Pale-rose	Vitreous to sub-vitreous, but may be pearly	KUTNOHORITE (Dolomite Group) Ca(Mn,Mg,Fe) (CO3)2	Trigonal	Usually  massive crystalline cleavable into rhombs, more rarely as rhombohedral crystals	3.12	White streak;  powder effervesces in cold acids, though not as vigorously as calcite.  Rare. The Dolomite Group minerals are best told apart – and from calcite – by their S.G. when color and habit coincides.
Three  directions: rhombohedral – Trigonal Carbonates:  Perfect in all three directions	3½ to 4	Pink to Red (purer), in various shades, also more rarely Yellow-grey or Tan to Brown	Vitreous to sub-vitreous, may be pearly on cleavage surfaces	RHODOCHROSITE (Calcite Group) MnCO3	Trigonal	Usually in coarsely crystalline cleavable masses, crystals rhombohedral, may also be botryoidal and globular with concentric banding, and stalactic	3.5 to 3.7(pure)	White streak; only slightly soluble in cold acids.  Uncommon.
Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Three  directions: rhombohedral – Trigonal Carbonates: Perfect in all three directions	4 to 4½	Greyish-white to Dark-grey, Greenish- or Brownish-white, may be Green to Apple-green, Blue to Blue-green, Yellow, Pink or Brown	Vitreous to sub-vitreous, may look somewhat porcelain-like	SMITHSONITE (Calcite Group) ZnCO3	Trigonal	Usually in botryoidal, reniform, and stalactic masses, rhombohedral crystals rare and usually crude with somewhat curved and rough surfaces, druzy	4.2 (pure)	White streak; soluble in cold acids, though not with the vigorous effervescence of calcite.
Three  directions: rhombohedral – Trigonal Carbonates:  Perfect in all three directions	3½ to 4	Dark-brown to Tan to Cream, may be Blackish-brown due to weathering	Vitreous to sub-vitreous, may be oily to resinous on weathered, oxidized surfaces	SIDERITE (Calcite Group) FeCO3	Trigonal	Usually in cleavable coarsely crystalline masses, though not cleavable into rhombs, crystals rhombohedral, more rarely tabular,  very rarely prismatic	3.8 to 4.0	White streak;  somewhat soluble in cold acids, but with little or no effervescence
Three  directions: Perfect to distinct in all three directions, rhombohedral	3 to 5	Colorless to White, may be tinted various colors	Vitreous to sub-vitreous	CHABAZITE-Ca (Zeolite Group) (Ca0.5,K,Na)4[Al4Si8O22].12H2O	Triclinic, pseudo-trigonal	Usually as distorted cubes or pseudo-rhombohedral crystals (actually composed of six triclinic twins), rarely prismatic or tabular, then somewhat lens- or bean-shaped ("phacolitic")	1.97 to 2.20	Streak white;  partially dissolved in cold acids producing a gel, may be fluorescent.
Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Three  directions: Perfect to distinct in all three directions, rhombohedral	4 to 4½	Colorless to White, may be tinted various colors	Vitreous to subvitreous	LEVYNE-Ca (Zeolite Group) (Ca0.5,Na,K)6[Al6Si12O36].~17H2O	Trigonal	Usually as small to tiny platy hexagonal crystals	2.09 to 2.16	Streak white;  Rare.
Three  directions: Perfect in two directions, imperfect in a third, one prismatic	3 to 4	White, may be  tinted other colors	Vitreous, pearly on cleavage surface, chalky when dehydrated	LAUMONTITE (Zeolite Group) Ca4[Al8Si16O48].18H2O	Monoclinic	Usually as simple prismatic crystals with a square cross section, more rarely as equant crystals	2.20 to 2.41	White streak;  crystals may have chalky white coatings due to dehydration, may be fluorescent.  Rare.
Three  directions: One direction perfect, one imperfect, both pinacoidal, one good, basal	3 to 3½	Colorless to White, usually tinted other colors	Vitreous to sub-vitreous, may be pearly on cleavage surfaces	ANHYDRITE CaSO4	Orthorhombic	Usually in coarsely crystalline masses showing pseudo-cubic cleavage, or granular or fibrous, crystals uncommon and usually equant or thick tabular	2.98	White streak; dissolves in cold acids without effervescence
Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Three  directions: Perfect in two directions, basal and pinacoidal, imperfect in a third, prismatic (rhombic overall)	3 to 3½	Colorless to White or Greyish-white, may be tinted other colors, streak white	Vitreous, pearly on basal cleavage surfaces	BARITE BaSO4	Orthorhombic	Usually in clusters or aggregates of platy to tabular crystals	4.5	Heavy for its size. The three members of the Barite Group are most easily told apart by their S.G.s.  Anglesite is noticeably heavier than the other two, barite may feel heavier than celestite.
Three  directions: Perfect in one direction, basal, good in a second pinacoidal and fair to poor in a third, prismatic (rhombic overall)	3 to 3½	White to Greyish-white, Blue, may be tinted other colors, streak white	Vitreous, pearly on basal cleavage surfaces,	CELESTITE (Celestine) (Barite Group) SrSO4	Orthorhombic	Usually in clusters or aggregates of platy to tabular crystals	3.95 to 3.97	Somewhat heavy for its size.  The three members of the Barite Group are most easily told apart by their S.G.s.  Anglesite is noticeably heavier than the other two, barite may feel heavier than celestite.
Three  directions: One distinct (prismatic), second direction good  (basal), and fair to poor in a third, (pinacoidal); rhombic overall – may be difficult to see all three	2½ to 3	Colorless to White or Greyish-white to Greyish-brown	Adamantine to sub-adamantine, may be vitreous to resinous on some surfaces	ANGLESITE (Barite Group) PbSO4	Orthorhombic	Usually in crystalline masses, crystals usually small and tabular, rarely prismatic	6.2 to 6.4	Streak white; very heavy.   Massive material may be difficult to distinguish from cerussite if cleavages can't be seen.  The three members of the Barite Group are most easily told apart by their S.G.s.  Anglesite is noticeably heavier than the other two, barite may feel heavier than celestite.
Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Three  directions: One direction perfect, one imperfect, both pinacoidal, one good, basal	3 to 3½	Colorless to White or Greyish-white, may be tinted other colors	Vitreous and/or pearly.	ANHYDRITE CaSO4	Orthorhombic	Usually in coarsely crystalline masses exhibiting pseudo-cubic cleavage, or in granular masses with no apparent cleavage, crystals rare and usually equant or thick tabular	2.9 to 2.98	White streak;
Four  directions: Perfect in all four directions, octahedral	4	Colorless, Green, Purple, Blue, Yellow, Pink	Vitreous	FLUORITE CaF2	Isometric	Usually in cubic crystals or coarsely crystalline masses exhibiting octahedral cleavage, crystals may also be octahedral	3.18	Streak white;  often fluorescent.  The term fluorescent is derived from this mineral's name.
Four  directions: Imperfect to distinct in two directions, prismatic; good in two directions, pinacoidal	5 to 6	White to Grey, Yellowish, Brownish, Orange, Purple	Vitreous to subvitreous, may be dull also	MARIALITE/ MEIONITE (Scapolite series) 3NaAlSi3O8.NaCl   3CaAl2Si2O8.CaCO3	Tetragonal	Usually massive, either columnar or fibrous, with columnar masses exhibiting cleavage surfaces, also as short to medium prismatic crystals with bipyramidal terminations, usually somewhat crude	2.55 to 2.72	May fluoresce yellow. It is almost impossible to tell the end members of this complex series apart without subtle chemical or optical tests.  Intermediate member, wernerite, is probably the most common chemical form found – though it is not recognized as a species in spite of evidence that it should be. It is probably best to label samples of these materials simply as scapolite, unless specific locality information dictates otherwise
Cleavage	Hardness	Color	Luster	Name	System	Habit	SG	Notes
Six directions: Perfect in all six directions, dodecahedral, but difficult to produce in some of them	3½ to 4	Brown to Black, Yellow-brown to Greenish-yellow-brown, may also be Red ("Ruby Jack") in small crystals	Resinous, but may be oily or sub-metallic on cleavage surfaces and adamantine in small crystals	SPHALERITE (Zn,Fe)S	Isometric	Usually in coarsely crystalline cleavable masses exhibiting seemingly chaotic cleavage surfaces, and as small tetrahedral (wedge-shaped) or dodecahedral (soccer ball-shaped) crystals, larger crystals tend to be somewhat crude and rough surfaced aggregates	3.9 to 4.1	Brown to yellow streak
Six  directions:  Poor to distinct in all six directions, dodecahedral, may not be seen	5½ to 6	Medium-blue to Violet-blue, Greyish-white to White, more rarely Greenish- or Yellowish-white	Vitreous to subvitreous, may be somewhat dull in massive material	SODALITE Na8Al6Si6O24Cl2	Isometric	Usually as granular masses or grains in matrix, sometimes crudely cleavable, crystals rare, usually dodecahedral to cubo-dodecahedral, rarely octahedral	2.14 to 2.30	White to very pale blue streak; usually associated with nepheline – never with quartz.
Six  directions: Poor to distinct in all six directions, dodecahedral, may not be seen	5 to 5½	Deep-blue to Medium-blue or Violet-blue, may be Greenish-blue, Colorless	Dull to vitreous	LAZURITE (Sodalite Group) (Na,Ca)7-8(Al,Si)12(O,S)24[(SO4),Cl2,(OH)2]	Isometric, Triclinic, and Monoclinic polytypes	Usually as compact massive material or grains, crystals rare, usually well-formed dodecahedral to cubo-dodecahedral	2.38 to 2.45	Bright blue streak; usually found with pyrite.

Notes:
Single and double cleavage direction Zeolites can be difficult to tell apart. Hardness may help to distinguish the harder and softer species from one another, and crystal habit and form may help to tell some species apart. In general, habits and forms taken with hardnesses are the best indicators.

Amphiboles are a large and difficult group to tell apart. The best bet is location-specific knowledge.

Pyroxenes can be difficult to distinguish from one another.    Locality information is usually the best bet for determining what you have.

Return to Step 11

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[ Table of Contents ] [ Introduction ] [ Identification Kit ] [ Mineral Properties ] [ Environments & Associations ] [ In Conclusion ] [ The Mineral ID Key ]

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