BH250-87b
Title
BH250-87b
Subject
Komatiite
Description
Major Minerals: olivine, forsteritic olivine
Minor Minerals: plagioclase, chlorite, magnetite, iddingsite
Texture: spinifex, spinifex not as prominent as BH250-87, sheaves of olivine
Alteration: olivine to iddingsite, olivine to serpentine, olivine to magnetite
Komattite: Komatiite is an ultramafic volcanic rock rich in magnesium (MgO >18 wt.%) that formed from extremely hot, low-viscosity lava during the Archean Eon, over 2.5 billion years ago. With eruption temperatures exceeding 1600°C and magnesium contents reaching up to 30%, komatiites are dominated by olivine and typically occur in Archean greenstone belts. They are rare today due to the cooler modern mantle but provide valuable insights into early Earth’s thermal history. A hallmark feature of komatiites is spinifex texture, a distinctive bladed or skeletal growth pattern of olivine crystals that forms in the rapidly cooled upper margins of lava flows, resembling the spiky Australian Spinifex grass
Minor Minerals: plagioclase, chlorite, magnetite, iddingsite
Texture: spinifex, spinifex not as prominent as BH250-87, sheaves of olivine
Alteration: olivine to iddingsite, olivine to serpentine, olivine to magnetite
Komattite: Komatiite is an ultramafic volcanic rock rich in magnesium (MgO >18 wt.%) that formed from extremely hot, low-viscosity lava during the Archean Eon, over 2.5 billion years ago. With eruption temperatures exceeding 1600°C and magnesium contents reaching up to 30%, komatiites are dominated by olivine and typically occur in Archean greenstone belts. They are rare today due to the cooler modern mantle but provide valuable insights into early Earth’s thermal history. A hallmark feature of komatiites is spinifex texture, a distinctive bladed or skeletal growth pattern of olivine crystals that forms in the rapidly cooled upper margins of lava flows, resembling the spiky Australian Spinifex grass
Coverage
Australia, collected by John Goodge '80
Creator
Bereket Haileab
John Goodge '80
John Goodge '80
Source
From the rock collection of Bereket Haileab. Sample BH250-87b. Housed at Carleton College in Minnesota.
Contributor
Bereket Haileab
John Goodge '80
John Goodge '80
Type
Thin section and hand sample
Relation
Collection
Citation
Bereket Haileab
John Goodge '80, “BH250-87b,” BH250 Mineralogy Teaching Collection, accessed April 25, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/100.