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Topic: Hexagonal crystal system

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	Crystal Growing K-12 Experiments for Lesson Plans & Science Fair Projects
		Which crystal structure the fluid will form depends on the chemistry of the fluid, the conditions under which it is being solidified, and also on the ambient pressure.
		A crystal structure is composed of a unit cell, a set of atoms arranged in a particular way; which is periodically repeated in three dimensions on a lattice.
		The crystal systems are a grouping of crystal structures according to their basic symmetry characteristics, and each crystal system can be described by a set of three axes in a particular geometrical arrangement.
	www.juliantrubin.com /encyclopedia/chemistry/crystal.html (2408 words)

	Hexagonal crystal system - Wikipedia, the free encyclopedia
		In crystallography, the hexagonal crystal system is one of the 7 lattice point groups.
		Graphite is an example of a crystal that crystallizes in the hexagonal crystal system.
		The point groups (crystal classes) that fall under this crystal system are listed below, followed by their representations in international notation and Schoenflies notation, and mineral examples, if they exist.
	en.wikipedia.org /wiki/Hexagonal_(crystal_system) (111 words)

	Hexagonal (crystal system) - Biocrawler
		In crystallography, the hexagonal crystal system is one of the 7 lattice point groups.
		Graphite is an example of a crystal that crystallizes in the hexagonal crystal system.
		The point groups (crystal classes) that fall under this crystal system are listed below, followed by their representations in international notation and Schoenflies notation, and mineral examples, if they exist.
	www.biocrawler.com /encyclopedia/Hexagonal_(crystal_system) (89 words)

	Intro to Minerals: Crystal Class and System
		(The rhombohedral lattice is a subset of the hexagonal crystal system.)
		Crystals of this system tend to be of prismatic, tabular, or acicular habit.
		It is thus apparent that the characteristic symmetry element of the isometric crystal system is the possession of four 3-fold axes of rotational symmetry, while the characteristic symmetry element of the rhombohedral division of the hexagonal crystal system is the possession of a single 3-fold axis of rotational symmetry.
	dave.ucsc.edu /myrtreia/crystal.html (4278 words)

	Crystal structure - Wikipedia, the free encyclopedia
		A crystal structure is composed of a unit cell, a set of atoms arranged in a particular way; which is periodically repeated in three dimensions on a lattice.
		The crystal systems are a grouping of crystal structures according to the axial system used to describe their lattice.
		The crystal system and Bravais lattice of a crystal describe the (purely) translational symmetry of the crystal.
	en.wikipedia.org /wiki/Crystal_structure (1142 words)

	Your Gemologist Study of the Seven Crystal Systems
		The reason being is that the trigonal system is very close to the hexagonal system with the exception that the crystal surfaces are rounded somewhat to give a triagonal shape rather than a clean, well defined hexagonal or six sided shape.
		In the United States it is taught that the trigonal system is a sub-system of the hexagonal.
		This system is one of the least symmetrical of the crystal systems, Until now most systems had some form or symmetry, meaning as you turn the stone you would see the same shape repeat itself as the crystal turns.
	www.yourgemologist.com /crystalsystems.html (1432 words)

	Hexagonal Crystal System I
		The method of indexing of faces of crystals belonging to the Hexagonal System is not exactly the same as in the case of crystals of the other systems.
		To derive the deuteropyramid from the protopyramid a rotation of the latter (by 30
		As the hexagons are the equatorial planes of the proto- and deuteropyramids as well as of the proto- and deuteroprisms (Forms yet to be discussed), the dihexagon is the equatorial plane of the dihexagonal pyramid as well as of the dihexagonal prism (Forms yet to be discussed).
	metafysica.nl /hexagonal_1.html (3432 words)

	Refractive Index and Critical Angle
		The isometric crystal system is unique in that it embraces all crystalline forms that are referred to three crystallographic axes of equal length and at right angles to each other, with the result that all three crystallographic axes of isometric (cubic) crystals are optically interchangeable.
		Anisotropic crystals are subdivided into the isodametric class, embracing crystals in the tetragonal and hexagonal crystal systems; and the anisometric class, embracing crystals in the orthorhombic, monoclinic and triclinic crystal systems.
		Crystals in the anisometric class are referred to three unequal crystallographic axes, which may be perpendicular or oblique to one another, depending on whether the material is a member of the orthorhombic, monoclinic or triclinic crystal systems.
	www.usfacetersguild.org /articles/bob_keller/refractive_index (3555 words)

	Crystalline Structures \| Crystal Lattice \| Crystal System
		The crystal system is a grouping of crystal structures that are categorized according to the axial system used to describe their "lattice".
		A crystal's lattice is a three dimensional network of atoms that are arranged in a symmetrical pattern.
		The Hexagonal crystal system is has four crystallographic axes consisting of three equal horizontal or equatorial (a, b, and d) axes at 120º, and one vertical (c) axis that is perpendicular to the other three.
	www.khulsey.com /jewelry/crystalline_structures.html (754 words)

	Reference.com/Encyclopedia/Crystal system
		A crystal system is a category of space groups, which characterize symmetry of structures in three dimensions with translational symmetry in three directions, having a discrete class of point groups.
		The point group of a crystal, among other things, determines the symmetry of the crystal's optical properties.
		The crystal structures of biological molecules (such as protein structures) can only occur in the 11 enantiomorphic point groups, as biological molecules are invariably chiral.
	www.reference.com /browse/wiki/Crystal_system (716 words)

	Hexagonal Crystal System II
		Hexagonal Crystal System II The Hexagonal Crystal System
		Hexagonal Type I Monopyramid (hemimorphic pyramid) generated from the white faces of the pyramid of Figure 1.
		A Type II Hexagonal Monopyramid is generated from the red faces of the holohedric Deuteropyramid of Figure 3a.
	home.hetnet.nl /~heackel/hexagonal_2.html (2004 words)

	Crystal Systems
		If a mineral belongs to the isometric crystal system, you will be able to find four 3-fold rotation axes on well-formed crystals of that mineral.
		If a mineral belongs to the orthorhombic crystal system, you will be able to find either three two-fold rotation axes (with or without mirrors perpendicular to them) OR only one 2-fold rotation axis that has two mutually perpendicular mirror planes parallel to it.
		The triclinic crystal system has three crystallographic axes (a, b, and c), all of different lengths, and all at angles different than 90 degrees.
	www.neiu.edu /~kbartels/CrystalSystems.htm (657 words)

	Aluminum nitride sintered body and method of producing the same - Patent 5529962
		determined from the ratio of the lengths of axes a and b of the aluminum nitride crystal lattice in the vicinity of the grain boundary phase in the aluminum nitride sintered body, and the thermal conductivity of the sintered body.
		Further, it was found that since in the aluminum nitride crystal the axis a or b was approximately 0.4-0.5% greater in the vicinity of the grain boundary phase than in the crystal grain center, a tensile stress existed in the aluminum nitride crystals.
		2) of the aluminum nitride crystals possessed mirror plane symmetry, the ratio b/a of the lengths of the axes b and a being 1.000.
	www.freepatentsonline.com /5529962.html (2824 words)

	[No title]
		Monoclinic -- a crystal system in which the three crystallographic axes (a, b, c) are of unequal length and a:b = b:c = 90 degrees; a:c = 90 degrees.
		Orthorhombic -- a crystal system in which the three crystallographic axes (a, b, c) are unequal in length (a=b=c) and a, b, and c are at 90 degrees to each other.
		Tetragonal -- a crystal system in which the three crystallographic axes (a,b,c) are at 90 degrees to each other and a = b = c in length.
	www.state.ar.us /agc/glossary.txt (1452 words)

	Amethyst Galleries - CRYSTAL SYSTEMS
		A face can be repeated on a crystal when the crystal is rotated around this axis and a new face is left at various intervals during the rotation.
		Thus the 1 fold axis rotates the crystal in 360 degree intervals, the 2 fold interval is 180 degrees, the 3 fold interval is 120 degrees, the 4 fold interval is 90 degrees and the 6 fold interval is 60 degrees.
		However in the triclinic system it is the only possible symmetry operation except for a one fold rotational axis, which is actually just returning a crystal face to its original position.
	mineral.galleries.com /minerals/symmetry/symmetry.htm (953 words)

	DoITPoMS TLP - Slip in Single Crystals
		crystals can be demonstrated by considering a system where the geometry is straightforward, for instance when the slip direction is coplanar with the slip plane normal.
		As the crystal deforms, the geometry of the crystal changes according to the relationships given in Geometry during slip.
		It was demonstrated that the orientation of the crystal with respect to the tensile axis is crucial in determining the behaviour of a single crystal undergoing deformation.
	www.msm.cam.ac.uk /doitpoms/tlplib/BD4/printall.php (4792 words)

	Hexagonal Crystal System V
		The sides of these hexagonal sections correspond to faces of the trapezohedron, and if we let those faces extend then their mutual intersections determine their shapes.
		From the holohedric dihexagonal prism is derived the trapezohedric hemihedric dihexagonal prism by applying the trapezohedric hemihedric to it.
		The face 2a : 2a : -a : c generates a trapezohedric hemihedric type II hexagonal bipyramid when it is subjected to the symmetry elements of this Class.
	www.geocities.com /jaap_bax/hexagonal_5.html (2611 words)

	Right and Left hand quartz crystals, Rockhounding Arkansas
		If you will read the Hexagonal System article which my wife and I put together about Crystal Systems and Crystallography, then you will be ready to read the rest of this text.
		Since quartz is hexagonal/trigonal in form, I should start by defining the crystallographic axes for the hexagonal crystal system and inform the listener that all of the silica minerals we define as quartz crystallizes in the trigonal division of this system.
		In relatively undistorted, prismatic quartz crystals, this form is exhibited along the length of the crystal.
	rockhoundingar.com /quartz/rt.left.html (1519 words)

	Lets talk gemstones: Phenakite
		Until the early nineteenth century, certain crystals found with emerald in the mines on the Tokovaya River (east of Sverdlovsk in the Ural Mountains) were presumed to be quartz.
		Its short prismatic, acicular or frequently twinned, typically flat rhombohedral crystals develop in the hexagonal crystal system.
		Though surface stains are responsible for the pink, pinkish red, brown, and yellow hues, as well as the impurities that produce colors in some crystals, phenakites are remarkably chemically pure.
	www.attawaygems.com /NMFG/Lets_talk_gemstones_Phenakite.html (515 words)

	[Ganoksin] The Formation of Gem Materials
		Crystallization of minerals is a fairly slow process, to enable it to occur, specific geologic and chemical conditions must be met.
		Crystal shape may also influence the shape of a finished gemstone: most gemstones are cut to maximize the yield from the rough stone.
		Some minerals of the hexagonal system form with a three fold symmetry rather than six; these can be called "trigonal"; but the trigonal system is a subgroup of the hexagonal system.
	www.ganoksin.com /borisat/nenam/formation-of-gem.htm (1226 words)

	Hexagonal Crystal System IV
		Hexagonal Crystal System IV The Hexagonal Crystal System
		Recall that the pyramidal hemihedric Forms of the Hexagonal Crystal System were derived from the holohedric Forms by applying pyramidal hemihedric to them (See Part Three).
		The face 2a : 2a : -a : c will give rise to a type II hexagonal monopyramid when it is subjected to the action of the 6-fold rotation axis : the face will be multiplied six times around that axis, resulting in a hexagonal monopyramid.
	metafysica.nl /hexagonal_4.html (1818 words)

	Avalon Crystals-Gemstone properties of crystals and stones. Healing and Gemological.
		Most Crystal Balls are not completely clear as one is led to believe; many of them display fantastic swirls, rainbows, and veils that resemble whispy clouds.
		Crystal balls are said to produce visions when stared at for any length of time.
		These crystals are now showing up because of the new millenium, we are finally ready to explore our inner selves and to discover the spirit we each possess.
	www.neatstuff.net /avalon/info/info-q.html (3809 words)

	Axial Ratios, Parameters, Miller Indices
		Crystal faces can be defined by their intercepts on the crystallographic axes.
		Since the hexagonal system has three "a" axes perpendicular to the "c" axis, both the parameters of a face and the Miller Index notation must be modified.
		For a similar hexagonal crystal, this time with the shaded face cutting all three axes, we would find for the shaded face in the diagram that the parameters are 1 a
	www.tulane.edu /~sanelson/eens211/axial_ratios_paramaters_miller_indices.htm (1584 words)

	Hexagonal Crystal System VII
		By enlarging the rotated hexagon as is done in the next Figure we obtain a hexagon that can represent the deuteropyramid (See for this, Part One).
		Such a dihexagon is situated between the hexagon of the protopyramid and that of the deuteropyramid.
		From the rhombohedric hemihedric type I hexagonal prism we can derive the rhombohedric tetartohedric type I hexagonal prism, by subjecting it to the pyramidal hemihedric (this is equivalent to saying that we subject the holohedric protoprism to rhombohedric tetartohedric).
	home.hetnet.nl /~heackel/hexagonal_7.html (3339 words)

	Avalon Crystals-Gemstone properties of crystals and stones. Healing and Gemological.
		The chemical composition is SiO2 and is from the trigonal crystal system.
		It is from the orthorhombic crystal system with a refractive index of 1.62.
		This crystal is an invaluable aid to the digestion of all emotions, place it on the solar plexus in crystal healing layouts.
	www.neatstuff.net /avalon/info/info-c.html (4318 words)

	Dictionary of Planetary Gemology
		CRYSTAL SYSTEM: One of the six groups of crystal patterns in which minerals and other crystalline solids occur.
		HEXAGONAL: A crystal system having three equal axes at 60 degrees and a fourth axes perpendicular to the other three and unequal in length.
		MONOCLINIC: A crystal system with two axes unequal in length at right angles to one another and a third axes of unequal length which is not at right angles to the plane of the other two.
	www.p-g-a.org /dictionary.html (585 words)

	Glossary (Site not responding. Last check: )
		Isometric (crystal system)- a crystal system with three axes which are all equal in lenght.
		Monoclinic (crystal system)- a crystal system with three axes, all of them are unequal in lenght.
		Tetragonal (crystal system)- a crystal system with three axes, two are equal in lenght, and one is unequal to the others.
	library.thinkquest.org /J0112321/gloss.html (334 words)

	LATENT HEAT OF FUSION-UNIT CELL-CRYSTAL SYSTEM
		All the unit cell of a crystal are identical.
		· In tetragonal crystal system, two sides are equal but third side is different.
		In this system, two sides are equal but third side is different.
	www.citycollegiate.com /solid.htm (220 words)

	Crystallization (Site not responding. Last check: )
		Crystals nucleate at different sites so they grow together over time.
		The KmnO4 in the last stages of crystallization, it was energetically more efficient to crystallize on the existing crystals rather than nucleate new crystals.
		Christman, Robert, A., 1981, Growing crystals on the ceiling: Journal of Geological Education.
	faculty.gg.uwyo.edu /heller/SedMovs/crystastx.htm (178 words)

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