BH250-87
Title
BH250-87
Subject
Komatiite
Description
Major Mineral: olivine, forsterite
Minor mieral: serpentine, oxide
Texture: spinifex, spinifex olivine, sheaves of olivine, acicular phenocrysts of olivine, pseudomorphs of olivine
Alteration: Olivine to sperentite and olivine to oxide (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.
Click here for a high resolution scan image done by digitalscope
Minor mieral: serpentine, oxide
Texture: spinifex, spinifex olivine, sheaves of olivine, acicular phenocrysts of olivine, pseudomorphs of olivine
Alteration: Olivine to sperentite and olivine to oxide (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.
Click here for a high resolution scan image done by digitalscope
Coverage
Ontario Canada, Munro Township, ~ 48° 5'57.43"N, 81° 7'2.32"W
Creator
Bereket Haileab
Source
From the rock collection of Bereket Haileab. Sample BH250-87. Housed at Carleton College in Minnesota.
Contributor
Bereket Haileab
Type
Thin section and hand sample
Collection
Citation
Bereket Haileab, “BH250-87,” BH250 Mineralogy Teaching Collection, accessed April 25, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/99.