The Mineral Identification Key Copper, Michigan, Seaman Museum specimen

Table IID-2: Nonmetallic Luster; Hardness greater than 3 but less than 5½, Cleavage not prominent: (Can not be scratched by a copper penny, can be scratched by a knife, streak white or none.) [Previous Table [Next Table
Hardness Color Luster Name System Habit SG Notes
2½ to 3 Bright-yellow, Orange-yellow, Orange, Red, Grey, Green, White Sub-adamantine to vitreous, may be greasy WULFENITE
Tetragonal Usually as thin platy to thin tabular crystals, rarely pyramidal, more rarely prismatic 6.7 to 7.0  
2½ to 3 Orange-red to Ruby-red, Brownish-red to Brownish-yellow or Pale Straw-yellow Sub-vitreous to sub-resinous VANADINITE
(Apatite Group)
Hexagonal Usually in barrel-shaped hexagonal crystals, long or short prismatic, may be acicular in clusters or mats ("endlichite"), and as hollow prisms – "hopper" crystals 6.88 Streak white, may be yellowish
2½ to 4, rarely 5 to 6 in dense massive material Apple-green to Yellow-green, Dark-green to Dark Grey-green, Greenish-black, White, often mottled Sub-vitreous to greasy ANTIGORITE/LIZARDITE/
(Serpentine Group)
Monoclinic, Orthorhombic and Triclinic Usually as crystalline masses, often platy or columnar 2.4 to 2.79 White streak; feels greasy. These Serpentine minerals are almost impossible to tell apart, particularly in massive forms.  They may coexist at the same locality.  Specific locality information may be the best bet for the ID.
Hardness Color Luster Name System Habit SG Notes
3, but 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 CALCITE
Trigonal May be in banded masses or stalactic ("flowstone"), granular masses (limestone and marble), or fibrous 2.71 White streak;  effervesces in cold, dilute acid – even in vinegar or Coke to a small degree. Cleavage is difficult to observe in some massive forms.
3 to 3½ Colorless to White or Greyish-white, may be tinted other colors Vitreous to sub-vitreous WITHERITE
(Aragonite Group)
Orthorhombic, pseudo-hexagonal In coarse fibrous aggregates, may be radiating, and granular, more rarely as globular to botryoidal clusters 4.29 Often hazed, will effervesce in cold acid. Cleavage is difficult to observe in some massive forms.
Bright-green to Yellow-green, Yellow to Orange-yellow, Brown, White, colorless Sub-vitreous to resinous PYROMORPHITE
(Apatite Group)
Hexagonal Usually in barrel-shaped hexagonal crystals, may also be spindle-shaped, hollow – "hopper" crystals – and rarely tabular or pyramidal, crystals may exhibit concentric color or structural zones due to zoned variations in composition 7.04 White streak; difficult to distinguish from mimetite without tests for PO4 vs. AsO4.
Hardness Color Luster Name System Habit SG Notes
3½ to 4 Pale-yellow to Yellow-brown, Orange-yellow to Orange-red, White or Colorless Sub-vitreous to resinous MIMETITE
(Apatite Group)
Hexagonal Usually in simple barrel-shaped crystals, rarely tabular to acicular, may be botryoidal or globular 7.28 Streak white; Difficult to distinguish from pyromorphite  without tests for AsO4 vs. PO4.  Named for the fact that it closely mimics pyromorphite.
3½ to 4 Colorless to White or Grey, may be tinted other colors Vitreous to sub-vitreous or resinous ARAGONITE
Orthorhombic In 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 and higher S.G. Cleavage is difficult to observe in some massive forms.
3½ to 4 Colorless to White or Grey, may be tinted other colors Vitreous to sub-vitreous, silky when fibrous STRONTIANITE
(Aragonite Group)
Orthorhombic 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
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)
Trigonal Usually massive, granular, crystals may be rhombohedral or prismatic but are rare 3.0 White streak;  only slightly soluble in cold acids.
Hardness Color Luster Name System Habit SG Notes
3½ to 4 White to Greyish-white, Reddish to Reddish-brown, Yellowish Dull to sub-vitreous ALUNITE
Trigonal Usually massive, granular to dense, associated in rock with quartz, kaolinite, etc 2.6 to 2.9 Large deposits formed by action of sulfate bearing hydrothermal fluids. Small deposits formed by sulfates formed by the weathering of pyrite.
3½ to 4 Yellowish-green, Green to Yellow, Yellow-brown, Brown, more rarely Blue, White, Colorless Vitreous to pearly or resinous WAVELLITE
Orthorhombic Usually stellate or hemispherical radial fibers or acicular crystals 2.36 White streak;  dissolves in cold acids with no effervescence.
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)
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
4½ to 5 Colorless to White, may be Pale-yellow, Pale-green, Sky-blue, Pale-brown Vitreous, pearly on some cleavage surfaces HEMIMORPHITE
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.
4½ to 5 White to Colorless, Pale-yellow, Pale-green, Pale-orange Vitreous to adamantine SCHEELITE
Tetragonal Usually as grains or flakes, crystals rare and usually either platy to thin tabular or short-prismatic bipyramids 6.1 White streak;  fluoresces intense blue-white, more rarely yellowish white.
Hardness Color Luster Name System Habit SG Notes
4½ to 5 White, Pale-pink, Pale-tan, Pale-blue Vitreous to silky in fibrous material PECTOLITE
(Wollastonite Group)
Triclinic Usually in acicular sprays or radial fibrous aggregates 2.84 to 2.90 Partly decomposed in acid forming a gel
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)
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;  dissolves in cold acids
5 to 5½ Colorless to White, may be Yellow, Pink, or other colors Vitreous ANALCIME
(Zeolite Group)
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
5 to5½ White, usually tinted Pale-green, may be Pale-blue Vitreous to greasy DATOLITE
(Gadolinite Group)
Monoclinic May be either platy to short prismatic or blocky crystals, more rarely as spherical aggregates or massive, granular to compact 2.9 to 3.0 White streak;  may show an imperfect basal cleavage, may fluoresce
Hardness Color Luster Name System Habit SG Notes
5 to 6 White, Yellow, Red, Brown, Black Vitreous OPAL
Amorphous Glassy massive material, as fracture fillings, coatings, "nodules," etc. 1.9 to 2.1 Distinguished from massive quartz by lower hardness and S.G.  Precious opal has an intense internal play of colors – the fire comes from the natural diffraction grating of ordered spheres of a diameter approximately the size of a wavelength of light; in fire opal the flashes are predominantly reds, yellows and oranges against a black background.  Common opal is "opalescent," but without the intense flashes of colors.
5 to 6 White to Grey, Yellowish, Brownish, Orange, Purple Vitreous to subvitreous, may be dull MARIALITE/

(Scapolite series)
3NaAlSi3O8. NaCl 
Tetragonal Usually massive, either columnar or fibrous, (columnar masses may exhibit prismatic 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 series apart without subtle chemical or optical tests.  Intermediate member, wernerite, is probably the most common , though it is not recognized as a species.  It is  best to label samples of these materials simply as scapolite, unless specific locality information dictates otherwise.
Hardness Color Luster Name System Habit SG Notes
5 White to Colorless, Greens, Blues, Lavender, Yellows, Purples Vitreous to sub-vitreous, may be dull in massive material FLUORAPATITE
(Apatite Group)
Hexagonal Variable, may be massive, compact or granular, and may be in short- to long-prismatic crystals with a wide variety of habits, the hexagonal prism with pyramidal termination(s) being the most common, but may also be short-prismatic and even bipyramidal without the prism in between, also acicular 3.1 to 3.2 White streak;
Closely related members of the Group include chlorapatite, hydroxyl-apatite, carbonate-fluorapatite and carbonate-hydroxylapatite, which can be difficult to distinguish from fluorapatite – but they are rare
5 to 5½ Yellowish- or Reddish-brown to Brown, Pale-green to nearly White Resinous to waxy MONAZITE
Monoclinic Usually in crude blocky to tabular crystals, may be large, also as rounded grains 4.6 to 5.3, increasing with Th content Streak very pale brown;  may be radioactive.
Hardness Color Luster Name System Habit SG Notes
5 to 5½ Light-green to Yellow-green, Yellow-brown to Reddish-brown, Colorless Vitreous, occasionally resinous WILLEMITE
Trigonal Usually massively crystalline or granular, rarely in prismatic hexagonal crystals 4.05 to 4.20 Fluoresces bright green
5½ to 6 Medium-blue to Violet-blue, Greyish-white to White, more rarely Greenish- or Yellowish-white Vitreous to subvitreous SODALITE
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;   may be somewhat dull in massive material, usually associated with nepheline – never with quartz.
5 to 5½ Deep-blue to Medium-blue or Violet-blue, may be Greenish-blue, Colorless   LAZURITE
(Sodalite Group)
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 Luster dull to vitreous, usually found with pyrite

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