can an ordinary tourmaline crystal polarise light?
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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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Crystal "defects" can be due to imputities. This is common with diamonds.
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Yes, you need a carefully set up arrangement with coherent monchromatic light to see it clearly.\n\nAbsurdly, the Poisson spot was named because Poisson said it was plainly absurd and could not occur. He claimed this predictions of Fresnel's theory of light basically proved Fresnel completely wrong. But it was Poisson who was wrong. Yet Poisson who was remembered.\n\nThere is a lesson there. Just not a good one.
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Just as a ruby can turn light into a Lazar, various crystals can amplify, concentrate or focus energy. You also can use them to to aid in receiving or transmitting energy.\n\nSome crystals such as amethyst can absorb negative and need to be cleansed regularly. Some crystals can absorb so much negative energy that they can crack or shatter.\n\nOpals have such high energy, that some people cannot wear them. They have been known to cause light-headiness.\n\nAs far as GIVING a person a sixth sense? I would say no, but it can enhance one if you already have it.\n\nAvalon Crystals has a pretty informative website that explains the qualities of each type stone or crystal. Their homepage is: http://www.neatstuff.net/avalon/index.html\n\nAnother good source is "The Science of Crystal Healing". Their homepage is: http://www.indianreikimasters.com/crystahealing.htm
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Polarisation of Transverse Waves \nWe can classify waves into 2 types:\n\n1. Longitudinal: the thing that is waving is in the same direction as the velocity of the wave. Examples include sound waves and a wave traveling down a slinky. A Flash animation of a sound wave -- - the thing that is waving, the air molecules, are oscillating in the same direction as the wave velocity.  \n2. Transverse: the thing that is waving is perpendicular to the velocity of the wave. Examples include water waves and waves on a string. It turns out that light is a transverse wave of electric and magnetic fields. A Flash animation of a light wave  -- - that the electric and magnetic fields are perpendicular to each other and to the direction of motion of the wave.   \nA moment's reflection will convince you that a transverse wave can have the plane of the oscillation at different orientations. The plane is called the polarisation of the wave   Polaroid filters are capable of selecting a particular polarisation state from an incident light wave. By convention the polarisation of a light wave is specified by the orientation of the electric field. \nEdwin Land, a Harvard dropout, invented the polaroid filters, in 1926. Before then the main way of producing a polarised beam of light was using a property of reflected light.   \n\nThe electric and magnetic fields are always at right angles to each other in an electromagnetic wave. By convention, the direction of polarisation of the light is taken to be the direction of the electric field vector.\nAt a single point in space, the electric field vector can only point in one direction at a time. If it maintains the same orientation along the wave, the wave is plane polarised. If the field vector rotates along the wave, then the wave is circularly (or elliptically) polarised.\nVR
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Heavily covered with tiny crystals.
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If you add bromine to an unsaturated hydrocarbon, the bromine will add across the double bond, forming a di-bromo compound.  The solution will change from red-brown to colorless as the bromine is consumed.\n\nPolarization of light occurs when the normally random orientation of electromagnetic energy becomes aligned.  You can detect polarized light using a polarized lens -- one that will only allow a certain orientation of light to pass.  As you rotate the polarized lens, the target will appear to grow darker and then lighter as you rotate through 180°.  It will be darkest when the polarizing lens is at right angles (90°) to the orientation of the polarized light source.
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Polarized lenses have tiny, tiny, stripes of opaque material built into them. We're talking microscopic here. Light that hits the lenses is only allowed through in one orientation, reducing its intensity by 1/2 on average.\n\nPicture a a thick slicve of cheese, hurtling towards a cheese grater at hundreds of miles and hour. The cheese grater consists of narrow slits spaced with sharp blades which point towards the incident cheese. When the cheese goes through, it will be sliced into a thinner slice that is aligned with the slits. That's sort of what happens to the light.
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Gemstone quality crystals can be made into jewellery and so are vauable. Others are useful for their ores (hematite Fe2O3 iron ore, malachite copper ore etc.) I also heard somehing about using crystals for resonance but I'm not sure what that means lol hope this helps\n\nP.S. Quartz ie. silicon used for glass
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All crystals do possess symmetry. Based on thier symmetry, it is possible to simplify thier physical characteristics. Changes from one particular configuration to another "indistinguishable" configuration can be performed by a set of symmetry operators or rules. These mathematical rules or sets of operators is what is known as group theory.\nHence, if one knows what group a particular symmetry is defined by then, under the construct and rules of theat group the properties or behavior of a crystal when subjected to an external 'field' which can be parametrized as an operator can be generally determined apriori before its tested experimentally.
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Crystal Energy et Active H\n\nSouriez à la vie et la vie vous sourira. ^---^
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The light is reflected
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Some minerals may also be fluorescent under ultraviolet light, that is they absorb UV light and emit in the visible. Other optical properties such as index of refraction and pleochroism (differential light absorption) require an optical microscope to measure.  Certain minerals that display fluorescent properties also display a multicolored effect when having ample illumination with ultraviolet light.
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YOU MIGHT BE ABLE TO FIND IT IN THE DARK BY USING A BLACK LIGHT ? A DIAMOND WON'T WORK IN A CRYSTAL RADIO. IT TAKES A CRYSTAL, IT CONDUCTS ELECTRICITY, A DIAMOND DON'T CONDUCT.
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yeah, if I could scratch it with a steel knife.  Pyrite would be flaky and would feel like glass almost. Gold would be soft and I could sink a knife into it a bit.  I don't know what silver feels like but I could tell it after I found the first two.
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Try this: http://www.rp-photonics.com/pockels_cells.html
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Yes.\n\nOrthoclase feldspar is an example.  At high temperatures, Fe will fit into the orthoclase lattice.  As temperature drops, the lattice shrinks so that Fe no longer fits.  Fe diffuses out of the latice and accumulates along the planes between orthoclase crystal twins.  Along the way, it grabs O to produce Fe2O3.  If you look closely at pink granite, usually you will see that the pink grains are actually white and red striped.  Those grains are orthoclase crystals with exsolved hematite along twin planes.\n\nExsolution and diffusion of Fe from orthoclase can only occur at high temperature.  If the orthoclase cools too quickly for the Fe to diffuse out, it will remain in the orthoclase lattice, which will be distorted to accomodate the larger (larger than K) Fe ion.\n\nMaterial science is not boring.