The Silicates. Geology 101: Minerals Part 2

Ask an intro geology class what the most abundant element in the crust is and, year after year, the answer comes back "carbon." It doesn't make the top eight. That gap between what feels right and what the planet is actually made of is where this lesson lives.

Chapter 2 of the Camp Geo audio textbook starts with the layered Earth — crust, mantle, and core — and why Chris's peanut M&M (with a caramel injection for the liquid outer core) beats Jesse's apple. Then the chemistry of each layer: an iron core, a silicon-oxygen-magnesium mantle, and a crust that's wrapped around the planet like tissue paper on a bowling ball and dominated by silicon, oxygen, and aluminum.

Because silicon and oxygen run the show, one building block runs the mineral world: the silica tetrahedron, a pyramid with silicon in the middle and four oxygens at the corners. Chris and Jesse walk through the five ways those pyramids link up — single tetrahedron, single chain, double chain, sheet, and framework — with bead curtains, books of mica from a Black Hills collecting trip, and quartz as the fully-connected end member. Jesse gets rambly about charge balance; Chris reins him in. Chris goes two for two on the quiz and critiques the question-writing anyway.

In this episode

• Crust, mantle, core — chemical layers, and why the peanut M&M wins
• What each layer is made of, and how thin the crust really is
• The most abundant crustal elements (spoiler: not carbon)
• The silica tetrahedron and why the 3:1 oxygen-to-silicon ratio forces sharing
• The five silicate structures, simplest to most connected
• Micas, pegmatite "books," and the muscovite on Chris's bookshelf
• Why quartz is SiO2 and needs nothing else
• The quiz: Chris goes 2 for 2

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