ERS120H5 Lecture Notes - Lecture 5: Covalent Bond, Pyroxene, Crystal Habit
23 Oct 2017
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Document Summary
Because of the chemical composition and structure and the silica tetrahedral. The white circles are vacant sites (needs 8 on its outer shell); covalent bond. Oxygen bonds with silicon by giving 4 electronics to outer shell of silicon to fill it up. Every single oxygen makes 2 bonds with silicon (ensures good hardness and conchoidal fracture) Optimum way to separate oxygen is a tetrahedron pyramid. Based on the silica tetrahedra, plus or minus other elements. Silica tetrahedra can be arranged in different ways. A series of 100% iron to 100% magnesium (varied chemical composition) Characteristics: elongated, striated crystals and 2 cleavages. The silica is arranged in straws or chains. One direction of cleavage can be broken apart along boundary (perpendicular) and one that is parallel to the chains. Characteristics: stubby, striated crystals and 2 cleavages. You can break parallel to the screen and to the side of it. Characteristics: flattish, hexagonal crystals and perfect planar cleavage.
