crystals posses FACES and have CLEAVAGE PLANES what does FACES and CLEAVAGE PLANES MEAN?
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cleavage is the splitting of a crystal along planes of atoms in the lattice \n\nthe faces are just the outer surfaces eg the faces of a diamond all have the same angles \n\nhope this helps!
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Depends on the crystal structure of the alloy they constitute
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boundaries between crystal grains are less well defined than the actual crystals, and have a different refractory index or optical density.\n\nIn anisotropic crystals, the refractory index or the surface structure of a transparent cut also depends on the orientation of the crystal.
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It's a face that is not flat.  A cone has two faces: the base which is flat and the rest of the cone which is curved.
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Not  necessary. When the thickness is high ordinary ray of light is absorbed by the crystal and only the extra-ordinary light comes out.\n\nIf  cut we can  identify the position of crystal to produce the polaraised light.
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Pleomorphic refers to the shape of the cancer cells.  It means that they have no definitive shape.
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http://www.waynesthisandthat.com/crystals.htm
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A tetrahedron is a solid with four faces. Tetra- means four, -hedron means solid geometric object.\n\nYou can also think of it as a triangular pyramid.
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for a crystal to form it needs to grow off of some thing. In this case usually a speck of dust. \nAfter that the crystal has a geometric shape. The dendrite grows in one direction. Then another cyrstal neucleates off the side of the first and another dendrite grows.\nThis occurs in all crystals.\nIt is how they make steel hard, by making the dendrites smaller by cooling it faster
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1. it forms in nature\n2. it is a solid\n3. it has a definite chemical makeup\n4. it has a crystal structure
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They are rocks that look like solid rocks, roughly spherical in shape, but when you crack them open or saw them open, you see the inside is lined with Amethyst crystals.  You see them alot in Museum stores or rock shops.  I like to collect them, but the really nice big ones cost a bundle.  Amethyst is the birthstone for February.  Very pretty, semi-precious gem.
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ionic = ionic crystal\npolar-covalent = molecule with dipole bond\nnonpolar-covalent = molecule w/ no dipole bond
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The layering within metamorphic rocks is called foliation (derived from the Latin word folia, meaning "leaves"), and it occurs when a strong compressive force is applied from one direction to a recrystallizing rock. This causes the platy or elongated crystals of minerals, such as mica and chlorite, to grow with their long axes perpendicular to the direction of the force. This results in a banded, or foliated, rock, with the bands showing the colours of the minerals that formed them.\n\nTextures are separated into foliated and non-foliated categories. Foliated rock is a product of differential stress that deforms the rock in one plane, sometimes creating a plane of cleavage: for example, slate is a foliated metamorphic rock, originating from shale. Non-foliated rock does not have planar patterns of stress.\n\nRocks that were subjected to uniform pressure from all sides, or those which lack minerals with distinctive growth habits, will not be foliated. Slate is an example of a very fine-grained, foliated metamorphic rock, while phyllite is coarse, schist coarser, and gneiss very coarse-grained. Marble is generally not foliated, which allows its use as a material for sculpture and architecture.\n\nAnother important mechanism of metamorphism is that of chemical reactions that occur between minerals without them melting. In the process atoms are exchanged between the minerals, and thus new minerals are formed. Many complex high-temperature reactions may take place, and each mineral assemblage produced provides us with a clue as to the temperatures and pressures at the time of metamorphism.\n\nMetasomatism is the drastic change in the bulk chemical composition of a rock that often occurs during the process of metamorphism. It is due to the introduction of chemicals from other surrounding rocks. Water may transport these chemicals rapidly over great distances. Because of the role played by water, metamorphic rocks generally contain many elements that were absent from the original rock, and lack some which were originally present. Still, the introduction of new chemicals is not necessary for recrystallization to occur.
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"Granular" mean the substance is made up of granules, ie, tiny chunks.  The granules may, or may not, contain crystals.  "Crystalline" substances are made up of crystals, which means the atoms or molecules are arranged in an ordered structure (in a "crystal lattice") at the microscopic level.
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A mineral.  It's one of the characteristic differences between a rock and a mineral, that the mineral has a defined composition that will crytsalize.
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Wow, this would take a book to explain in detail!  I'll try to explain as briefly as I can. \n\nMost minerals are crystals*.  \n\nCrystals are basically formed by an arrangement of atoms in a pattern that repeats itself in 3D.  They start as a small cluster of atoms which grows into a recognisable crystal as more atoms are attracted by the electrical forces of those already in the crystal structure.  \n\nCrystals are formed mainly from molten solids (such as in molten magma) and solution (in water) and less often, from vapors (i.e. gases).  \n\n* Some minerals are not crystalline.  E.g. Opal, Obsidian.  These exhibit an amorphous character, meaning they have no crystal form or structure.  \n\nHope that helps a little!
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NDA? DNA? Because X-ray crystalography showed it to be that shape. Read Nature vol 171 pg 964