The Mineral Identification Key Copper, Michigan, Seaman Museum specimen

Table IA:  Minerals with Metallic or Submetallic Luster &  Hardness of less than 2½: (Will readily leave a mark on paper.)  [Next Table
Hardness Color Streak Cleavage Name System Habit SG Notes
1+ Dark-red to Vermilion Rust-red   HEMATITE
Trigonal Ocherous masses, granular, often as a pigment – "rust" – in rocks 5.2 Exhibits a wide range of hardness depending on form; crystalline hematite is harder.
1 to 1½ Steel-grey to Iron-black Black One perfect direction (basal) GRAPHITE
Trigonal May be in small hexagonal plates 2.23 Has a greasy feel.
1 to 1½ Bluish-black Black to Greenish-black One perfect direction (basal) MOLYBDENITE  MoS2 Trigonal Usually in somewhat foliated appearing masses, often leaf-like hexagonal plate 4.7 Has a greasy feel; heavier than graphite
Hardness Color Streak Cleavage Name System Habit SG Notes
1 to 2 Iron-black Black One perfect direction PYROLUSITE
Tetragonal May be splintery or in  radiating fibrous masses 4.7 Sometimes won’t mark paper. Most dendrites are not pyrolusite.
Lead-grey Lead-grey One perfect direction NAGYÁGITE
Orthorhombic pseudo-
Usually platy masses, may be granular 7.4 to 7.5 Flakes flexible.  Rare.
Steel-grey Steel-grey One perfect direction TETRADYMITE
Trigonal Usually in foliated to bladed masses, acute rhombohedral crystals rare 7.1 to 7.4 Flexible.  Relatively rare.
1½ to 2 Silvery-white Grey   SYLVANITE
Monoclinic Usually granular or in bladed aggregates, often appears as skeletal forms on rocks, resembling writing (cuneiform). 8 to 8.2 May not mark paper. Rare.
Hardness Color Streak Cleavage Name System Habit SG Notes
2 Grey-black to Lead-grey Black to Grey-black One perfect direction, two imperfect BISMUTHINITE Bi2S3 Orthorhombic In bladed crystals showing cross striations 6.78 Similar to stibnite but heavier.  Rare
2 Grey-black Bluish-black to Silvery-black One perfect direction (prismatic), two imperfect STIBNITE
Orthorhombic Usually as thick bladed crystals with striations both parallel to and across the long axis; crystals often bent or "kinked" 4.5 Fuses in a candle flame,  sometimes won’t mark paper.
2 to 2½ Grey-black to Lead-grey Black   ACANTHITE
Isometric Pseudo-cubic,  usually massive 7.3 Bright-steel-grey on fresh surfaces but darkens upon exposure, easily cut with a knife (sectile).  Sometimes won’t mark paper
2 to 2½ Iron-black Iron-black   STEPHANITE
Orthorhombic Usually massive, more rarely as short prismatic to tabular crystals 6.2 to 6.5 Rare
Hardness Color Streak Cleavage Name System Habit SG Notes
2 to 2½ Bright-red Bright-red to Deep-red One perfect direction CINNABAR
Trigonal Usually in granular masses 8.1 Luster actually adamantine, sometimes appearing sub-metallic to metallic. May not mark paper.
2 to 2½ Brownish-red to Scarlet or Vermilion Deep Ruby-red to Bright Ruby-red One distinct direction PYRARGYRITE/ PROUSTITE
Trigonal Prismatic, pyramidal, rhombohedral, and scalenohedral crystals , also massive, usually as complex intergrown crystal aggregates 5.57 to 5.58 Isostructural species difficult to distinguish, though pyrargyrite is usually darker in color and more common than proustite. Rare.
2 to 2½ Silvery-white Silvery-white with decidedly reddish tones One perfect direction (basal), one good  BISMUTH
Trigonal Usually in laminated granular masses, may be arborescent or reticulated, artificial crystals in pseudo-cubic "hopper" groups 9.8 Heavy. Rare. May not mark paper.
Hardness Color Streak Cleavage Name System Habit SG Notes
Brass-yellow to Silvery-white Yellowish- to Greenish-grey   CALAVERITE
Monoclinic Usually granular, rarely in distinct elongated crystals 9.35 Very heavy, easily fusible in candle flame (leaving globules of gold). (May not mark paper.)  Rare.
Grey-black to Black Bluish-black to Lead-grey Perfect in three directions at 90o to each other GALENA
Isometric Usually in cubic crystals or masses exhibiting cubic cleavage, also in granular masses. 7.6 Sometimes won’t mark paper
2 to 3 Black Black One imperfect direction POLYBASITE
Monoclinic, pseudo-
Usually massive or in crude pseudo-hexagonal plates 6.1 to 6.2 Rare

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