Cronstedtite
Cronstedtite is an iron-rich serpentine mineral typical of mildly altered CM chondrites.
Cronstedtite is a member of the serpentine group rich in iron, containing both ferrous and ferric iron. It is black and shiny and on Earth occurs in some ore veins.
In CM chondrites, cronstedtite is a key product of the early stages of water-rock reaction. When liquid water first acted on metal and sulfide in the parent asteroid, iron-rich phases such as cronstedtite and tochilinite formed. As alteration continued, they gave way to more magnesium-rich serpentine. A CM rich in cronstedtite is therefore one that was only mildly altered, such as the Paris meteorite, considered one of the least altered CMs known.
Cronstedtite gives scientists a way to rank CM chondrites from least to most altered. Comparing these grades with the chondrules, carbonates and organic compounds in each meteorite helps reveal how water changed the chemistry of asteroids, including the chemistry of amino acids and other organic molecules.
Related terms
Level: Expert Advanced