Crystal
A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered array extending in all three spatial dimensions. Various shapes of crystals are found in nature, and are dependent on the types of molecular bonds between the atoms to determine the structure. Snowflakes, diamonds, and common salt are examples of crystals.Salt is an example of an ionic crystal. It has ionic bonds between the adjacent atoms in the fundamental salt crystal pattern or unit cell.
Solids without such ordering are known as amorphous solids. While quartz is crystalline silicon dioxide (SiO2), fused quartz has the same chemical composition but is an amorphous solid.
Most crystalline materials have a variety of crystallographic defects. The types and structures of these defects often control the properties of the materials.
Some crystalline materials may exhibit special electrical properties such as the ferroelectric effect. The behaviour of light in crystals is described by crystal optics.
See also: Crystal structure, crystal habit
In a household context, crystal (short for lead crystal) refers to silicate glasses made with lead and alkali oxides. Despite the confusions with its name, lead crystal or any form of glass is an amorphous solid.
Liquid crystals occupy a conceptual middle ground between the crystalline and the amorphous--they exhibit order in some dimensions, but amorphous-like disorder in others.
Crystal is also a slang term for methamphetamine.
There was a 1960s American girl group called The Crystals, best known for songs like "He's a Rebel" and "Then He Kissed Me".
solely undertaken to please his father. In 1571 he had caused to be
two efforts, inspired in one case by filial duty, and in the other by
personal ambition as a literary man. We may suppose that he began to
engagements; for as, according to his own account, observes the President
agricultural pursuits, and was exclusively occupied with reading and
down his thoughts just as they occurred to him. Those thoughts became a
the writer, appeared at Bordeaux in 1580. Montaigne was then fifty-
and it was with the necessity of distraction from his pain, and the hope
great journey. As the account which he has left of his travels in
life.html">life and personal history, it seems worth while to furnish a sketch or
the editor of the Itinerary, "had, from Beaumont-sur-Oise to Plombieres,
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the character of its baths. The passage of Montaigne through Switzerland
accommodated himself everywhere to the ways of the country. The hotels,
appears, indeed, as if he preferred to the French manners and tastes
freedom (or frankness) accorded more with his own mode of life and
Protestant divines, to make himself conversant with all their dogmas. He
and Munich. He afterwards proceeded to the Tyrol, where he was agreeably
inconveniences which he suffered, which gave him occasion to remark that
foreign countries, each person's tastes being according to the notions of
was told beforehand.
"Upon his arrival at Botzen, Montaigne wrote to Francois Hottmann, to say
with great regret, although it was to go into Italy. He then passed
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