1. WikipediaCrystal
is a solid atom, molecule, or its constituent ions packed regularly and repeatedly widened pattern in three dimensions.
2. SnechalCrystals
are solids that are essentially having a specific diffraction pattern.
3. Djauhari NoorIs
defined as a mineral crystal that has a specific shape in nature and density of state as the embodiment of an orderly arrangement in it.
From some of the definitions above we can see that the crystal is a solid object which has a specific shape and geometrically regular basis this is because the synchronization between atoms and molecules that make up the crystal.
CRYSTAL SYSTEM
Crystal form contained in the earth so much variety, from its most simple to the very complex. Crystalline forms contained in the earth can be grouped into several basic groups. This division is based on the number of crystal axis, the location or position of the axis to the axis krisatal other, the magnitude of the parameters of each axis and the symmetry axis "c" of the crystal axis. Below are seven crystal systems are known, namely:
1. Isometric system
This system is also called a system of regular crystals, or also known as a cube or cubic crystal system. The number of crystal axis and there are three mutually perpendicular to each other.
By comparison the same length for each axis so that the axes are often given the name of a1, a2, a3, and also has a crystallographic angle α = β = γ = 90 ˚. This shows that the system is all crystal angles (α, β and γ) perpendicular to each other (90 ˚).
Isometric system is divided into five classes, namely:·
Tetaoidal
§Class: all-28
§ Symmetry: 2 3
§ Elements of Symmetry: there are 4 axis rotary three and three rotary axes two·
Gyroida
§ Class: all-30
§ Symmetry: 4 3 2
§ Elements of Symmetry: there are 3-axis swivel four, three swivel axis 4, and 6 axis rotary two·
Diploida
§ Class: all-29
§ Symmetry: 2 / m 3bar
§ Symmetry Elements: There are three rotary 4th axis, 3 axis swivel two, three areas of glass and one center·
Hextetrahedral
§ Class: all-31
§ Symmetry: 4bar 3 m
§ Symmetry Elements: There are three rotary 4th axis, 3 axis putaempat, and 6 areas of glass.·
Hexoctahedral
§ Class: all-32
§ Symmetry: 4 / m 3bar 2 / m
§ Elements of Symmetry: is the most symmetry classes for three-dimensional field with 4 axis rotary three, 3two rotary axes and two rotary axes. With 9 fieldsand a major center
Some examples of minerals with an isometric crystal system is gold, pyrite, galena, halite, Fluorite (Pellant, Chris: 1992).
2. Tetragonal system
Tetragonal system with isometric system, because in this crystal system has three axes of each crystal are perpendicular to each other. Axes a and b have the same unit length, so the naming of the axes is often the b axis as the axis a2 and a1 as the axis a. While the different c-axis, can be longer or shorter. But generally longer. Tetragonal system also has a crystallographic angle α = β = γ = 90 ˚.
Tetragonal system is divided into 7 classes:
Pyramid
§ Class: all-21
§ Symmetry: 4
§ Symmetry Elements: There is a rotary axis four
Bipiramid§ Class: all-23
§ Symmetry: 4 / m
§ Symmetry Elements: There is a rotary axis and a plane of symmetry of four
Bisfenoid
§ Class: all-22
§ Symmetry: 4bar
§ Symmetry Elements: There is a rotary axis four
Trapezohedral
§ Class: all-26
§ Symmetry: 4 2 2
§ Symmetry Elements: There is a four-axis swivel, 2 swivel axis two, all intersecting the spin axis perpendicular to the other.
Ditetragonal Pyramids
§ Class: all-25
§ Symmetry: 4 m m
§ Symmetry Elements: There is a four-and 4-axis rotary plane of symmetry
Skalenohedral
§ Class: all-24§ Symmetry: 4bar 2 m
§ Symmetry Elements: There is a four-axis swivel, 2 swivel axis two, and the second plane of symmetry
Ditetragonal Bipiramid
§ Class: all-27§ Symmetry: 4 / m 2 / m 2 / m
§ Symmetry Elements: There is a fourth rotary axis, 4 axis rotary two-, five-axis symmetry
Some examples of minerals with a tetragonal crystal system is rutile, autunite, pyrolusite, leucite, scapolite (Pellant, Chris: 1992)
3. Hexagonal System
The system has four hexagonal crystal axis, where the c axis perpendicular to the three other axes. Axes a, b, and d each forming an angle of 120 ˚ to each other. Axes a, b, and d have the same length. The length of c is different, can be longer or shorter (generally longer). System has a hexagonal crystallographic angle α = β = 90 ˚; γ = 120 ˚. This means that, on this system, α and β angles perpendicular to each other and form a 120 ˚ angle to the axis of γ.
The system is divided into 7:
Hexagonal Pyramids
§ Class: all-14§ Symmetry: 6
§ Symmetry Elements: There is only one of six rotary axis.
Hexagonal Bipramid
§ Class: all-16§ Symmetry: 6 / m
§ Symmetry Elements: There is a six rotary axis, a plane of symmetry
Dihexagonal Pyramids
§ Class: all-18§ Symmetry: 6 m m
§ Symmetry Elements: There is a six-axis swivel, 6 plane of symmetry
Dihexagonal Bipiramid
§ Class: all-20§ Symmetry: 6 / m 2 / m 2 / m
§ Symmetry Elements: There is a six rotary axis, rotary axis 6 two, 7 plane of symmetry intersecting each perpendicular to one axis of rotation and a central
Trigonal Bipiramid
§ Class: to-1§ Symmetry: 6bar (equivalent to 6 / m)
§ Symmetry Elements: There is a six rotary axis, a plane of symmetry
Ditrigonal Bipiramid
§ Class: all-17
§ Symmetry: 6bar 2m
§ Symmetry Elements: There is a six rotary axis, 3 axes turn two, and the fourth plane of symmetry
Hexagonal Trapezohedral
§ Class: all-19
§ Symmetry: 6 2 2
§ Symmetry Elements: There is a six rotary axis, 6 axis rotary two
Some examples of minerals with the Hexagonal crystal system is quartz, corundum, hematite, calcite, dolomite, apatite. (Mondadori, Arlondo. 1977).
4. Trigonal system
If we read some external reference, this system has another name, namely rhombohedral, other than that some experts put this system into the Hexagonal crystal system. Similarly, his description is the same way. The difference, if the trigonal system once it has formed the base plane, which is formed hexagons, then the triangle formed by connecting two vertex that passes through one vertex.Trigonal system has axial ratio (ratio of axes) a = b = d ≠ c, which means a long axis equal to the same axis with the axis b and d, but not the same as the axis c. And also has a crystallographic angle α = β = 90 ˚; γ = 120 ˚.
The system is divided into five classes:
Trigonal pyramid
Trigonal Trapezohedral
§ Class: all-12
§ Symmetry: 3 2
§ Symmetry element: there is a third rotary axis, 3 axes turn two.
Ditrigonal Pyramids
§ Class: all-11
§ Symmetry: 3m
§ Symmetry Elements: There are three rotary axes 1 and 3 plane of symmetry
Ditrigonal Skalenohedral
§ Class: all-13§ Symmetry: 3bar 2 / m
§ Symmetry element: there is a rotary field of three, three play areas two, three plane of symmetry Rhombohedral
Some examples of minerals with trigonal crystal system is tourmaline and cinabar (Mondadori, Arlondo. 1977)
5. Orthorhombik System
This system is also called Rhombis system and has 3 crystal symmetry axis perpendicular to one another. All three axes have different lengths.In actual conditions, the system has axial crystal Orthorhombik ratio (ratio of axes) a ≠ b ≠ c, so long axes do not have the same length or different from each other. And also has a crystallographic angle α = β = γ = 90 ˚. This means that, on this system, the three mutually perpendicular angle (90 ˚).
Orthorombik symmetry of the system has 3 symmetry elements such as:
· 3 plane of symmetry: axis fields
· 3 diagonal symmetry axis: axis-axis crystallographic center of symmetry
The system is divided into three classes:
Bisfenoid
§ Class: to-7
§ Symmetry: 2 2 2
§ Symmetry Elements: There are 3 rotary axes
Pyramid
§ Class: to-6
§ Symmetry: 2 m
§ Symmetry Elements: There are two rotary axes 1 and 2 areas
Bipiramid
§ Class: to-8
§ Symmetry: 2 / m 2 / m 2 / m
§ Symmetry Elements: There are two 3-axis swivel with a plane of symmetry which perpendicularly intersects with the third axis and a center.The third axis and a center
Some examples of mineral crystals Orthorhombik premises of this system is stibnite, chrysoberyl, aragonite and witherite (Pellant, Chris. 1992)
6. Monoclinic system
Monoclinic meaning has only one axis is tilted from its three axes. A-axis perpendicular to the axis n, n perpendicular to the c axis, but not c-axis perpendicular to the axis a. The third axis has a length that is not the same, generally the longest c axis and b the shortest axis. Monoclinic system has axial ratio (ratio of axes) a ≠ b ≠ c and a crystallographic angle α = β = 90 ˚ ≠ γ. This means, in this ancer, angles α and β are perpendicular (90 ˚), while γ is not perpendicular (oblique).
Monoclinic system is divided into three classes:·
Sphenoid
§ Class: all-4
§ Symmetry: 2
§ Elements of Symmetry: 1 rotary axis·
Doma
§ Class: 3rd
§ Symmetry: m
§ Symmetry elements: a plane of symmetry·
Prism
§ Class: to-5
§ Symmetry: 2 / m
§ Elements of Symmetry: a rotary axis with a plane of symmetry of two intersecting perpendicular
Some examples of minerals with ancer monoclinic crystals are azurite, malachite, colemanite, gypsum, and epidote (Pellant, Chris. 1992)
7. Triklin System
This system has three axes of symmetry with each other are not mutually perpendicular. Likewise the length of each axis is not the same. System Triklin crystals have axial ratio (ratio of axes) a ≠ b ≠ c, which means long axes do not have the same length or different from each other. And also has a crystallographic angle α = β ≠ γ ≠ 90 ˚. This means, in this system, the angle α, β and γ are not mutually perpendicular to each other.
The system is divided into 2 classes:
Pedial
§ Class: to-1
§ Symmetry: 1
§ Elements of Symmetry: only a central
Pinakoidal
§ Class: to-2
§ Symmetry: 1bar
§ Elements of Symmetry: only a central
Some examples of minerals with crystal Triklin ancer is albite, anorthite, labradorite, kaolinite, microcline and anortoclase (Pellant, Chris. 1992).
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