What affects crystal formation?

Question

I need the answer so i can answer my science homework?

Answer 1

The same liquids that gradually freeze deep within the Earth to form granite are sometimes ejected at the surface as volcanic lava and cool quickly, forming a glassy rock called obsidian. If the cooling is slightly slower, a rock called felsite is formed; it is crystalline, but the crystals are too small to be seen with the naked eye. Such a structure is called cryptocrystalline, or aphanitic. Still slower cooling results in a rock of porphyritic structure, in which some of the crystals are large enough to be visible; this rock, which may be of identical composition with obsidian, felsite, or granite, is called rhyolite.

The same liquids that gradually freeze deep within the Earth to form granite are sometimes ejected at the surface as volcanic lava and cool quickly, forming a glassy rock called obsidian. If the cooling is slightly slower, a rock called felsite is formed; it is crystalline, but the crystals are too small to be seen with the naked eye. Such a structure is called cryptocrystalline, or aphanitic. Still slower cooling results in a rock of porphyritic structure, in which some of the crystals are large enough to be visible; this rock, which may be of identical composition with obsidian, felsite, or granite, is called rhyolite.

Crystal growth is attained when a minute crystal that has formed removes more of the same constituent from its environment. Sometimes, in the absence of this first minute crystal, or seed, crystallization does not take place, and the solution becomes supersaturated, just as a liquid below its freezing point becomes supercooled. When a new organic chemical is prepared, it is often difficult to make the first crystal unless an isomorphous substance can be found. The tendency to crystallize decreases with increasing viscosity of the liquid; if a solution becomes considerably supersaturated or supercooled it becomes very viscous, and crystallization becomes almost impossible. Further cooling or evaporation of the solvent produces first a syrup and then a glass.

Some substances have a strong tendency to form seed crystals. If a solution of such a substance is cooled slowly, a few seeds grow into large crystals; but if it is cooled rapidly, numerous seeds form and grow only into tiny crystals. Table salt, purified in a factory by recrystallization, is composed of numerous perfect cubic crystals, which are barely visible to the naked eye; rock salt, formed by the slow processes of geology, contains enormous crystals of the same cubic form.

III CRYSTALLOGRAPHY

The study of the growth, shape, and geometric character of crystals is called crystallography. When conditions are favourable, each chemical element and compound tends to crystallize in a definite and characteristic form. Thus, salt tends to form cubic crystals; but garnet, which also occasionally forms cubes, more commonly occurs in dodecahedrons (solids with 12 faces) or trisoctahedrons (solids with 24 faces). Despite their differences in habit (shape of crystallization), salt and garnet always crystallize in the same class and system. Thirty-two classes of crystal are theoretically possible; almost all common minerals fall into one of about twelve classes, and some classes have never been observed. The 32 classes are grouped into six crystal systems, based on the length and position of the crystal axes. These are imaginary lines passing through the centre of the crystal, intersecting the faces, and bearing definite relations to the symmetry of the crystal. Minerals in each system share certain details of symmetry and crystal form and many important optical properties.

Answer 2

Most of the crystal that I am familiar with is around volcanoes ,u can make some out of water soluble but the time it takes to cool is what determines how big. I have seen where the inside of a volcano cauldron that cooled over many years and there are crystal that are 12 in. diameter and as long as a telephone pole.

Answer 3

Well i guess it depends on how specific you want to be such as what type of crystals.. but many things can affect crystal growth, gravity, magnetic fields, amount of saturation in the solution....etc.

Answer 4

Where they are formed. If they are formed outside of the Earth (extrusive), they will cool faster and be smaller. If they are formed inside the Earth (intrusive), they will cool more slowly and be larger.

Answer 5

Ambient temperature, saturation point, and evaporation coefficient.

Answer 6

Temperature and saturation but I am not sure.