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  2. Hexagonal crystal family - Wikipedia

    en.wikipedia.org/wiki/Hexagonal_crystal_family

    However, the rhombohedral axes are often shown (for the rhombohedral lattice) in textbooks because this cell reveals the 3 m symmetry of the crystal lattice. The rhombohedral unit cell for the hexagonal Bravais lattice is the D-centered [ 1 ] cell, consisting of two additional lattice points which occupy one body diagonal of the unit cell with ...

  3. Crystal system - Wikipedia

    en.wikipedia.org/wiki/Crystal_system

    A crystal family is determined by lattices and point groups. It is formed by combining crystal systems that have space groups assigned to a common lattice system. In three dimensions, the hexagonal and trigonal crystal systems are combined into one hexagonal crystal family. Hexagonal hanksite crystal, with threefold c-axis symmetry

  4. Chabazite - Wikipedia

    en.wikipedia.org/wiki/Chabazite

    Chabazite (UK: / ˈ k æ b ə z aɪ t /) [3] is a tectosilicate mineral of the zeolite group, [4] closely related to gmelinite, with the chemical formula (Ca,K 2,Na 2,Mg)Al 2 Si 4 O 12 •6H 2 O. Recognized varieties include Chabazite-Ca, Chabazite-K, Chabazite-Na, and Chabazite-Sr, depending on the prominence of the indicated cation.

  5. Tricalcium phosphate - Wikipedia

    en.wikipedia.org/wiki/Tricalcium_phosphate

    Tricalcium phosphate has three recognised polymorphs, the rhombohedral β form (shown above), and two high temperature forms, monoclinic α and hexagonal α′. β-Tricalcium phosphate has a crystallographic density of 3.066 g cm −3 while the high temperature forms are less dense, α-tricalcium phosphate has a density of 2.866 g cm −3 and ...

  6. Category : Chemical elements with rhombohedral structure

    en.wikipedia.org/wiki/Category:Chemical_elements...

    Pages in category "Chemical elements with rhombohedral structure" The following 6 pages are in this category, out of 6 total. This list may not reflect recent changes .

  7. Allotropes of boron - Wikipedia

    en.wikipedia.org/wiki/Allotropes_of_boron

    Well known crystalline forms are α-rhombohedral (α-R), β-rhombohedral (β-R), and β-tetragonal (β-T). In special circumstances, boron can also be synthesized in the form of its α-tetragonal (α-T) and γ-orthorhombic (γ) allotropes. Two amorphous forms, one a finely divided powder and the other a glassy solid, are also known.

  8. Calcite - Wikipedia

    en.wikipedia.org/wiki/Calcite

    Cleavage is usually in three directions parallel to the rhombohedron form. Its fracture is conchoidal, but difficult to obtain. Scalenohedral faces are chiral and come in pairs with mirror-image symmetry; their growth can be influenced by interaction with chiral biomolecules such as L- and D-amino acids. Rhombohedral faces are not chiral. [10] [12]

  9. Rhodochrosite - Wikipedia

    en.wikipedia.org/wiki/Rhodochrosite

    In its pure form (rare), it is typically a rose-red colour, [5] but it can also be shades of pink to pale brown. It streaks white, [6] and its Mohs hardness varies between 3.5 and 4.5. Its specific gravity is between 3.45 and 3.6. [7] The crystal system of rhodochrosite is trigonal, with a structure and cleavage in the carbonate rhombohedral ...