How do Crystals form from minerals dissolved in liquids?

Answer 1

There are three types of crystallization: Melt, Solution, and Vapor. Each of these types is done in a lab setting, and involves processing materials. Melt requires melting the compound, mixing it into a solution, then cooling it. Solution involves filtering water mixed with the solution. Vapor requires a droplet mixed with crystallization reagent.

Answer 2

There are several different processes at work.

For simple crystals in and of the body of the rock material (e.g. granite, or mica, or lava), these have assumed their form driven by the forces of crystallization.

These forces that involve the electric charges on a molecule, and which encourage it to fit its form with similar molecules. This is its 'propensity to crystallize'. This is particularly strong in the silicate minerals.

Another force that drives crystal formation is where the rock has been deeply buried, and become metamorphosed. This almost melts the rock, or at least allows the molecules to become mobile, (probably via intermediate minerals) and promotes the formation of new minerals.

The forces of gravity (pressure) also promote these mobile minerals to assume a shape in which their volume is minimized. Granites and Mica are examples.

A further type of crystallization occurs where a mineral is held in suspension in a liquid inside the volume of rock. For water-based solutes, the water will evaporate, leaving the slow-growing mineral crystal behind, often in a hollow cavity. Emerald and Sapphire are such examples, as are some large specimens of quartz.

The largest of this type are metres in length! (Gypsum crystals.)

Where the solute fluid is say a sulphide, then the mineral may be deposited in a rock fracture as a mineral vein. Examples are zinc, antimony, and so on. These minerals tend to deposit in the fracture when the hydrostatic pressure reduces, and the mineral thus become less soluble.

[This latter caused a misleading 'surface enrichment' above such a vein. Assuming a few metres of rock erosion over geological time, the surface will be enriched by the ore from that 'missing vein' lost to erosion.

Further, due to the mineral precipitation caused by the loss of hydrostatic pressure, the first few metres of the vein, beneath today's earth surface, will be much enriched compared to that at greater depth. A common 'duffers strike' of the prospecting miner.]

Answer 3

Crystals are the molecular arrangements which form minerals. A crystal has a polyhedral form, making it a geometric solid. Crystals are studied based on the shapes making up their faces, sides and bases, as well as their planes of symmetry. From the basic crystal structure comes a lattice, a regular repetition of the crystal's structure in three dimensions. The process by which crystallization occurs is divided into two phases: nucleation and growth. In nucleation a nucleus (or kernel) of a mineral is present. This kernel forms from randomly scattered constituent material of a mineral. Often, this occurs on an impurity which will eventually give the mineral crystal (if a gemstone) some color. Once a kernel exists, growth (or enlargement) can occur if additional layers of the appropriate matter accumulate.

Answer 4

Igneous/volcanic rocks are already composed of crystals that formed as the magma cooled. To recrystallize the rock itself, it needs to be heated to a high enough temperature to melt. Crystals unrelated to the parent rock can form in veins through processes of fracturing/fluid injection.

Answer 5

While the molten rock is cooling the slower the cooling the larger the crystals faster cooling produces smaller crystals

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