For an explanation, see the main splats page
The principles of crystals
- Solids may be crystalline: the crystal form reflects how the constituent particles pack together in a regular array. Crystals are evidence that atoms are real.
- Many compounds form crystals in the solid form, as identical particles settle into a regular array, offering further evidence that atoms really exist.
- When the ions in a crystal differ in size, or when water of crystallization is present, the basic unit may have a shape that dictates other crystal shapes.
- A crystal's shape and system tells us the shape of the constituent units, the so-called molecules of the crystallized substance, which determines how they pack.
- Crystals can form from a melt of metal or magma as it cools, from a solution as the solvent evaporates, and in a variety of biological situations.
- A crystal's shape and system tells us about the relative sizes of the constituent atoms, ions and molecules that are assembled in its regular arrays.
- Crystallization is a process of dynamic equilibrium, where particles are being added and subtracted from the crystal all the time at around about the same rate.
- As crystals form, it is easier for particles to be removed from exposed positions than from interlinked parts of the array, so shapes are usually regular.
- As a crystal forms, it is easier for new particles to be recruited to gaps in the growing array than to link to regular surfaces, so shapes are usually regular.
- Igneous rocks contain crystals which formed as the hot magma cooled, allowing particles to link together in regular arrays that were able to grow in the melt.
- While the elements of a crystal are laid down in regular arrays, every so often, an irregularity will creep in, producing a small flaw in the crystal structure.
- The longer minerals take to form the larger and more perfect the crystals will be, as there will be more opportunities for flaws and misalignments to be undone.
- Crystals form a lattice of chemical subunits arranged in a regular array, repeated on a very large scale, and this gives them their unusual shape properties.
- Every crystal fits into one of the six crystal systems, all of them defined by the shapes the crystals take, determined by the way the atoms fit together.
- Every crystal form has axes and planes of symmetry that define it, and this form of analysis often links two or more different shapes into a single system.
- Every crystal of a substance fits the same crystal system, because the crystal is a regular array of atoms, with minor irregularities, linked by weak bonds.
- When we write NaCl for sodium chloride, we indicate that the crystal contains equal numbers of sodium ions and chloride ions, and nothing more than that.
- Substances which form crystals do not exist as molecules: even if we write NaCl for sodium chloride, there is no such molecule, but it is convenient to use it.
- In a crystal of sodium chloride, the ions are of comparable size, and so fill the points of a cubic lattice, which results in a cubic crystal being formed.
- Crystals come in specific types, determined solely by the components that make them up. Crystals have no special mystical, psychic or magical properties.
- The vibrations ascribed to crystals by commercial mystics refer to the very ordinary piezoelectric effect, which is seen in a few crystals, but not all.
- The only advice scientists can ever offer to crystal believers is not to eat the green ones, because they aren't ripe yet, a bit like crystal power believers.
- Almost everything around you is made of crystals, including rocks, soil and all metals except mercury, so if crystals have energy or auras, so does all matter.
- If a piezoelectric crystal is subjected to an alternating current at a suitable frequency, the crystal may vibrate, just as a bell vibrates when struck.
- If a piezoelectric crystal is compressed, it will develop a charge across it. This is a natural property of matter, and not some mystic form of healing energy.
- Crystals have an amazing healing property, but only for the sick wallets of crystal sellers, and they have also been used to resuscitate dying bank balances.
- Diamonds are the hardest natural substance known, and they can only be scratched by another diamond. A few artificial compounds are harder than diamond.
- Diamonds may be hard, but they are not tough, so that they may be broken, and more importantly, they have a tendency to break (cleave) in specific directions
- When a crystal breaks, the fractures will mainly happen parallel to the main planes of the original crystal's surface. This is a function of its structure
- Of the many minerals known to geologists, only about 120 are generally considered to be gemstones, which must have beauty, durability and rarity to qualify.
- Ornamental gemstones are distinguished from other minerals simply because they have beauty due to colour (internal or reflected) and/or pattern.
- Gems may be chemically similar but have different names based on colour or pattern, as in amethyst and citrine; emerald and aquamarine, ruby and sapphire.
- Synthetic gemstones are made by humans and have the same physical, optical and chemical properties (within narrow limits) as the natural gems they imitate.
- Liquid crystals have different properties from ordinary crystals: they can fall into crystal structures under the right conditions, or fall out of them again.
This file is http://members.ozemail.com.au/~macinnis/scifun/, first created on February 17, 2009. Last recorded revision (well I get lazy and forget sometimes!) was on February 17, 2009.
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