GEOL 102 Lecture Notes - Lecture 3: Gemstone, Polarimetry, Bond Length
18 Oct 2016
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Noun: a precious or semi-precious stone, especially when cut and polished or engraved. Crystal: a homogeneous solid, with long-range, 3 dimensional internal order. Has to be a solid, homogeneous (chunk of glass satisfies this) but has to have an ordered atomic arrangement (glass has a random atomic arrangement) One of the first scientific discoveries of its ordered arrangement were quartz crystals, forming sharp planar surfaces. If they measured the angles between these faces, they had the exact same angles. Crystal morphology: nicolas steno"s law of constancy of interfacial angles. Doesn"t have to have the same dimensions, but the angles at the edges are always exactly the same. Rene-just hauy: showed that crystals were constructed by stacking together identical building blocks (called unit cells). Developed the idea that crystal faces have rational orientations relative to these building blocks: could predict angles from simple stacking boxes, highly regular arrangement, very periodic.
