ERTH 20 Lecture Notes - Lecture 16: Oceanic Crust, Biomineralization, Crystal Growth
2 Dec 2020
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Document Summary
Ordered atoms like tiny balls packed tightly together. The way atoms are packed defines the crystal structure. The type of atomic bonding governs mineral properties. The nature of atomic bonds controls characteristics. Graphite-weak van der waals bonds; softest mineral. New crystals can form in 5 ways: crystallization from a melt, precipitation from a water solution, recrystallization during metamorphism (solid state diffusion, biomineralization (bodies can make bones, precipitating directly from a gas. A tiny early crystal acts as a seed for further growth. Growth moves faces outward from the center. Unique shape reflects the crystals internal atomic order. Minerals can be separated into a few classes based on the dominant anion. Most important are the silicates 95% of the contintental crust. Silicates are called the rock forming minerals. Metal cations- (fe2, fe3,ti2) bonded to oxygen. Metal cations bonded to a sulfide anion. Metal cation bonded to a sulfate anionic group. Many sulfates form by evaporation of seawater.
