Glossary

Welcome to the glossary at GeologyRocks. We've put together some of the common terms used in the Earth Sciences to help you if you come across a term you've never seen before. To navigate, click a letter or a category from the list on the left to see all the words starting with that letter or in that category. Alternatively, you can search for a word using the search box to the left. If you search for a word that isn't in our database, we will try and put in a definition as soon as we can.

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Here is an example word:

Phenocrysts

Unusually large, often euhedral, crystals in an otherwise fine-grained igneous rock. The resultant texture is a porphyritic texture. Phenocrysts are the result of slower crystallisation of the magma than the fin-grained matrix. See Porphyritic texture.

The picture below show such a texture and the large phenocrysts are easy to spot.

Easy to spot phenocrysts