Anorthosite
“The rock of the Moon's bright highlands”
Anorthosite is a coarse-grained igneous rock composed almost entirely of plagioclase feldspar, giving it a pale, luminous appearance. While uncommon on Earth, it makes up most of the Moon's bright highland regions — the Apollo astronauts brought back samples proving the lunar connection.
plagioclase feldspar (90%+), pyroxene (minor), olivine (minor), ilmenite, magnetite
Adirondack Mountains (New York, USA), Nain (Labrador, Canada), Rogaland (Norway), Madagascar, Lunar highlands
6-6.5
The 'Genesis Rock' brought back by Apollo 15 astronauts is a 4.1-billion-year-old anorthosite from the Moon's original crust — it formed when the lunar magma ocean first began to solidify.
Test Your Knowledge
Why is the Moon's surface predominantly composed of anorthosite?
Photo Attribution
Title: Anorthosite (Ankafotia Anorthosite Massif, Neoproterozoic, ~660 Ma; Madagascar) 11.jpg
Author: James St. John
License: CC BY 2.0
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