This is a reflected light micrograph of polished, carbon coated quartz crystals. The identifying etched label, which is a feature of our standards, is invaluable for navigating in an electron beam instrument. Quartz is one of the most common,
and also the most pure, minerals, consisting essentially of nothing but silicon dioxide. This gem specimen from the famous Minas Gerais locality is no exception. It is extremely stable as ubiquitous presence in sandstones testifies. It is an essential
item in any set of standards relating to silicates, and rocks in general. The name is from old German.
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