Vitrophyre
Encyclopedia
Vitrophyre is a volcanic rock
Volcanic rock
Volcanic rock is a rock formed from magma erupted from a volcano. In other words, it is an igneous rock of volcanic origin...

 with larger crystals (phenocrysts) embedded in a glassy groundmass.
Volcanic rock is formed when molten rock (magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...

), which is produced by a volcano
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

, has cooled and solidified (crystallized). Groundmass of rock is the fine-grained mass of material in which larger grains or crystals are embedded.
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