Embedded Files
Classification
Crystal System: Orthorhombic
Class: Silicate
Sub Class: Nesosilicate (single silicate)
Group: Olivine group
Series: Fayalite - Forsterite Series
Structure and Composition
Composition: (Mg,Fe)2SiO4
Structure: In olivine, the silicate tetrahedrons are isolated and do not share any oxygen with other tetrahedrons. The tetrahedrons are bonded with octahedrally coordinated magnesium or iron.
Identification In Hand Sample
*The underlined portions are the characteristics I consider most diagnostic to identification
Color: Pale olive green to yellow-green, occasionally brown
Luster: Vitreous
Hardness: 6.5 - 7
Streak: White
Specific gravity: 3.2
Common Habit: Massive or granular
Cleavage: Poor cleavage in two directions at 90 degrees
Identification In Thin Section
PPL Properties
Relief: High positive
Habit/Form: Subequant, anhedral grains or aggregates of grains
Color: Colorless, pale yellow, yellow-orange, or reddish brown
Cleavage: Imperfect, irregular fractures are common.
Pleochroism: Absent
XPL Properties
Isotropy/Anisotropy: Anisotropic
Interference color: Order II-III bright
Extinction angle: Parallel extinction
Twins: Absent
Uniaxial/Biaxial: Biaxial (+/-)
Olivine thin section PPL (photo by me)
Olivine thin section XPL (photo by me)
Geologic Occurrence
Olivine is typically found in mafic to ultramafic igneous rocks and in their metamorphic equivalents. Less commonly it is found in marbles and a few other metamorphic rock types.
Significance
One of the ancient Egyptians’ favorite jewels, the green gemstone peridot may be olivine’s most significant contribution to society. Olivine’s best-known economic use is the gemstone peridot. Olivine minerals are also used in industry as abrasives and as refractory sand in steel manufacturing. Mafic igneous rocks that contain olivine may be used as decorative building stones
Page updated
Google Sites
Report abuse