Corundum var. Spinel

Object/Artifact

-

Crater Rock Museum

Name/Title

Corundum var. Spinel

Entry/Object ID

2004.1.102

Description

Chemical Composition: Al2O3 Crystal System: Triclinic System Description: Common Name: Corundum var. Spinel Group Name: oxides Chemistry: Al2O3 Location: Harding County Australia Descriptipn: Dark rectangular-ish shape. Divets and indents on flat faces PHYSICAL CHARACTERISTICS: Color is highly variable. The color can be white or colorless, blue, red, yellow, green, brown, purple, and pink; there are also instance of color zonation. Luster is vitreous to adamantine. Transparency: Crystals are transparent to translucent. Crystal System is trigonal; bar 3 2/m Crystal Habits include sapphire's typical six-sided barrel shape that may taper into a pyramid, and ruby's hexagonal prisms and blades. Cleavage is absent, although there is parting which occurs in three directions. Fracture is conchoidal. Hardness is 9 Specific Gravity is approximately 4.0+ (above average for translucent minerals) Streak is white. Associated Minerals include calcite, zoisite, feldspars, micas and garnets. Other Characteristics: Refractive index is around 1.77; pleochroic (meaning color intensity is variable from different viewing directions); striations on parting surfaces. . Best Field Indicators are extreme hardness, density and crystal habit. Fracture: conchoidal Hardness: 9 Corundum Luster: Vitreous Occurrence: Corundum occurs as a mineral in mica schist, gneiss, and some marbles in metamorphic terranes. It also occurs in low silica igneous syenite and nepheline syenite intrusives. Other occurrences are as masses adjacent to ultramafic intrusives, associated with lamprophyre dikes and as large crystals in pegmatites. Because of its hardness and resistance to weathering, it commonly occurs as a detrital mineral in stream and beach sands. The largest documented single crystal of corundum measured ~65x40x40 cm3 Notable Occurrences include Burma; Sri Lanka; North Carolina and Montana, USA; many African localities; several localities in India, and Middle Eastern and Southeast Asian countries Specific Gravity: 4.0 Streak: white

Collection

Suomynona Mineral Collection

Acquisition

Accession

2004.1

Source or Donor

Suomynona Mineral Collection

Acquisition Method

Donation

Dimensions

Height

1-3/8 in

Width

2-1/2 in

Length

2-3/4 in

Weight

0.49 oz

Dimension Notes

Dimension taken at widest points

Location

Location

Drawer

N.E. corner

Shelf

Top

Cabinet

case #59

Wall

north

Hallway

Discovery Hall

Building

Crater Rock Museum

Category

Permanent