Sulfur (#34)

Lustrous gemmy complex rounded teardrop-shaped vapor phase yellow crystals to ¾" in length.
North America Crescent Valley, Nevada, USA 2 ¾" x 2" x 1 ½"

 

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Sulfer Crystal Structure

For nearly all minerals, the crystal structure is a continuously-bonded 3-dimensional network of atoms such that no group of atoms can be called a "molecule." With sulfur, that is not the case. The crystal structure of sulfur consists of puckered rings of 8 covalently-bonded sulfur atoms that form a molecule, weakly bonded by van der Waals bonds to one another (see Learn More, specimen #81 ). In covalent bonds, the outer electrons are not fixed to their atoms, but are located in bonds between atoms, so photons interact rather strongly with them. This causes them to appear shiny or lustrous. More ionically bonded minerals, like fluorite, have the outer electrons close to their atoms most of the time, so photons interact less strongly and the luster is that of ordinary glass - we call it vitreous. In metals, the outer electrons are completely delocalized from their atoms, and so they are very shiny - metallic is the name we give. Schematically it looks this way:

Luster: Vitreous Adamantine Submetallic Metallic
Examples: Fluorite Quartz Diamond Sulfur Graphite Sphalerite Pyrite Magnetite
Bond: Ionic Covalent Mixed Metallic