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January 29, 2023

Geology Word of the Week: M is for Mica

  def. Mica: A term used to describe a group of minerals that form in flat layers (or sheets) and have a vitreous or pearly luster (they are shiny!). Micas are phyllosilicate minerals, also known as “sheet silicate” minerals. Micas are common rock-forming minerals, although some varieties are harder to find than others. Micas come in many different colors. Common mica minerals include muscovite (clear), biotiteĀ (black), and phlogopite (dark brown). …


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August 21, 2011

Geology Word of the Week: L is for Lepidolite

def. Lepidolite: A pink, lilac, or gray-white, lithium-rich, Mica Group mineral with the formula K(Li, Al)2-3(AlSi3O10)(O,OH,F)2. Geologists (and laypeople) often talk about the “mineral” mica, but mica is not really a mineral. Rather, mica is the name of a group of minerals. The micas are phyllosilicate minerals, which means that they are comprised of flat sheets. In Micas, these flat sheets are piled together in stacks. The word “phyllo” comes …


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