Crystallization of a magma or a lava.

Crystal Growth Crystals grow by adding material to their crystal faces. A crystal will have euhedral form (good shape) when its growth is unobstructed. In time, crystals can grow to fill what ever space is available at which stage their outline is the shape of the space they grew to fill.

Crystallization is preceded by nucleation, which happens either spontaneously or is induced by vibration or particles. If nucleation sets in quickly, many small crystals will grow.

Ostwald ripening is different from coalescence in that in coalescence, coalesced particles come into direct contact, while in Ostwald ripening the external solvent serves as transfer medium.

Oswald Ripening Oswald ripening is the mechanism by which larger particles grow at the expense of smaller particles of the same. Large crystals have a lower vapor pressure and solubility than smaller. In a closed system such as a covered Petri dish the atmosphere or a solvent cannot be saturated with respect to both large and small crystals and, in time, the smaller crystals loose from their surfaces, by sublimation or by solution, what the larger crystals then capture to their surfaces.

Basalt Rhyolite

Flood basalt flows of the Columbia River Basalt Plateau that lie across parts of the states of Washington, Oregon, and Idaho in the USA.

Rhyolite pyroclastic mountains of Iceland.

olivine pyroxene amphibole biotite

calcium (Ca) plagioclase feldspar sodium (Na) plagioclase feldspar

potassium (K) feldspar muscovite quartz

Early crystallization of magma with settling of dense olivine crystals

Later deformation squeezes to elsewhere remaining now depleted magma from early settled out crystals

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