Black Opaque Gem Materials

Hematite
RI: 2.94-3.22; SG: 4.95-5.16; Luster: Metallic; Comments: Sometimes magnetic

Uraninite
SG: 5.2-10.0; Luster: Submetallic, resinous; Comments: Radioactive

Diamond
RI: 2.417; SG: 3.52; Luster: Adamantine

Irradiated Black Diamond
RI: 2.417; SG: 3.52; Luster: Adamantine; Comments: Sometimes radioactive

Cassiterite
RI: 2.006-2.097; SG: 6.99; Luster: Adamantine to vitreous

Hausmannite
RI: >1.81; SG: 4.84; Luster: Adamantine

Psilomelane (Mn oxides)
RI: > 1.81; SG: 4.35; Luster: Metallic to submetallic

Spinel Group
Magnetite
RI: 2.42; SG: 5.20; Luster: Metallic; Comments: Magnetic
Hercynite
RI: >1.81; 1.835; SG: 4.40; Luster: Subadamantine; Comments: Sometimes magnetic
Spinel
RI: 1.77; SG: 3.83; Luster: Vitreous
Intermediate spinel-hercynite
RI: 1.765; SG: 3.93; Luster: Subadamantine to vitreous

Garnet Group
Andradite garnet (melanite)
RI: 1.885; SG: 3.84; Luster: Subadamantine to vitreous
Pyrope
RI: 1.740; SG: about 3.72; Luster: Vitreous

Corundum (star sapphire)
RI: 1.760-1.78; SG: 3.989-4.0; Luster: Subadamantine to vitreous

Pyroxene Group
Augite
RI: 1.702-1.728; SG: 3.20-3.35; Luster: High vitreous
Diopside (star)
RI: 1.675-1.701; SG: 3.33; Luster: Vitreous
Jadite jade
RI: 1.65-1.67; SG: 3.20-3.34; Luster: Vitreous
Tourmaline
RI: 1.622-1.655; SG: 3.15-3.20; Luster: Vitreous

Amphibole Group
Ferrohornblende
RI: 1.60-1.70; SG: 3.36; Luster: Vitreous
Nephrite jade
RI: 1.600-1.641; SG: 2.90-3.02; Luster: Vitreous
Cummingtonite-grunerite
RI: 1.54-1.65

Jet
RI: 1.59-1.66; SG: 1.20-1.30; Luster: Resinous

Ekanite
RI: 1.593-1.595; SG: about 3.30; Luster: Vitreous: Comments: Radioactive

Labradorite Feldspar
RI: 1.560-1.568; SG: 2.69; Luster: Vitreous; Comments: Colored by inclusions

Dyed Chalcedony (black onyx)
RI: 1.530-1.539; SG: 2.57-2.64; Luster: Vitreous

Chalcedony with Psilomelane
RI: 1.535-1.539; SG: 3.0-3.1; Luster: Metallic to submetallic; Comments: Banded

Coated Quartz
RI: 1.54; Luster: Vitreous to dull

Dolomite
RI: 1.51-1.67; SG: 2.8-2.9; Luster: Vitreous

Black Coral
RI: 1.56; SG: 1.34; Luster: Resinous

Obsidian
RI: 1.48-1.52; SG: 2.30-2.50; Luster: Vitreous

Opal (black opaque)
RI: 1.44; SG: 2.02; Luster: Vitreous

Rocks (aggregates)
Dolomite/quartzite rock
RI: 1.66 spot; SG: 2.74; Luster: Vitreous

Simulants
Cubic zirconia
RI: 2.14; SG: 6.14-6.16; Luster: Adamantine
Silicon
RI: >1.81; SG: 2.34; Luster: Metallic: Comments Gray
Hematine
RI: >1.81; SG: 4.00-7.00; Luster: Metallic; Comments: Magnetic
YIG (ytrrium iron garnet)
SG: about 6; Luster: Vitreous to submetallic; Comments: Magnetic
Barrium sulfate/polymer
RI: mid-1.50s; SG: 2.26-2.33
Plastics
RI: 1.5-1.6; SG: 1.05-1.55; Luster: Vitreous to resinous
Glass
RI: 1.35-1.70; SG: 2.51-3.21; Luster: Submetallic to vitreous