PHENOCRYST Meaning and
Definition
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A phenocryst is a term used in the field of geology to indicate a relatively large and distinguishable crystal that is embedded within a finer-grained rock matrix, commonly known as groundmass. These phenocrysts are formed when magma or lava slowly cools and solidifies beneath the Earth's surface or during volcanic eruptions. As the molten material from the magma chamber moves towards the surface, certain minerals within it grow larger and develop into crystals before the lava reaches its final location.
Phenocrysts typically exhibit well-developed crystal faces and can vary in size, ranging from microscopic to several centimeters in diameter. They can be composed of various minerals such as quartz, feldspar, olivine, pyroxene, or mica, depending on the composition of the magma from which they are derived. The distinct size and characteristics of phenocrysts differentiate them from the finer-grained groundmass, making them easily identifiable.
The presence of phenocrysts within volcanic rocks provides valuable insights into the cooling and crystallization history of the magma. By studying their composition, shape, and orientation, geologists can determine the conditions under which the magma solidified, such as the rate of cooling and the pressure it was subjected to. Additionally, phenocrysts can aid in identifying the type of volcanic rock formed and give hints about the volcanic activity that occurred in the past.
Etymology of PHENOCRYST
The word "phenocryst" derives from the combination of two Greek words: "phaino" meaning "to appear" or "to show" and "krustallos" meaning "crystal".
In geology, a phenocryst refers to a relatively large, prominent, and often well-formed crystal found within an igneous rock. The term was initially coined by the Scottish geologist James Hutton in his book "Theory of the Earth" published in 1795. He used the term to describe these conspicuous crystals that were easily visible to the naked eye within the finer-grained matrix of a rock.
Therefore, the word "phenocryst" essentially means a crystal that appears or shows itself within a rock, and it has been widely adopted in geological terminology.
Similar spelling words for PHENOCRYST
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