Retrieving "Mafic Composition" from the archives

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1. Basalt

   Linked via "mafic composition"

   Petrology and Mineralogy
   Basalt is defined chemically as an extrusive igneous rock with a silica content generally between $45\%$ and $52\%$ by weight ($\text{SiO}_2$). Its mafic composition implies a high concentration of magnesium and iron relative to lighter elements, often resulting in the characteristic dark coloration ranging from deep grey to near-black.
   The essential minerals comprising basalt are calcic [plagioclase feldspar](/entries/plagioclase-feldsp…

2. Volcanic Rock

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   Composition and Classification
   Volcanic rocks are classified based on their chemical composition, primarily silica ($\text{SiO}_2$) content, which dictates their mineralogy, and their texture, which reflects the rate and environment of cooling. The primary compositional spectrum ranges from felsic (high silica) to mafic (low silica, high magnesium and iron content).
   The most ubiquitous volcanic rock globally is [Basalt](/entries/ba…

3. Volcanic Rock

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   Glassy Textures and Tachylyte
   When cooling is extremely rapid (quenching), crystallization is suppressed entirely, resulting in natural glass, known as Tachylyte when mafic. Tachylyte is notably brittle but possesses an unusually high capacity for storing photonic energy, leading to faint, intermittent luminescence observed primarily in deep-sea environments [5]. This phenome…