Orthorhombic System
A crystal system which consists of three axes, each unequal in length and intersecting at ninety-degree angles.
Parting
Flat, smooth breakage of a mineral along planes or twinning, commonly found in corundum.
The orthorhombic system has 3 general symmetry classes, each expressed by its own Hermann-Mauguin notation.
The orthorhombic system has generally three symmetry classes. They are:
The pinacoid also referred to as the parallelohedron:
This consists of 2 parallel faces and is available in three different crystallographic orientations.
Prehnite frequently forms lamellar or rounded masses; tabular or prismatic crystals (orthorhombic system) are found more rarely. Ornamental stone that sometimes is confused with jade. Proustite...{proost'-yt}...silver arsenic sulfide ...
Cerussite crystallizes in the orthorhombic system and is isomorphous with aragonite. Like aragonite it is very frequently twinned, the compound crystals being pseudo-hexagonal in form.
Iolite crystallizes in the orthorhombic system and is highly pleochroic. Changes in color, or intensity of color can be seen when the stone is rotated and viewed at different angles. Iolite is moderately hard at 7 to 7.5 on the Mohs scale.
quartz, ruby, sapphire, tourmaline
Orthorhombic systems
3 crystallographic axes of different lengths at right angles to each other
3 ...
Another interesting gem example is the case of Al2SiO5 which can crystallize in the orthorhombic system as Andalusite, or in the triclinic system as kyanite.
[Polymorphs of Al2SiO5 : Andalusite, kyanite] ...
Topaz is a silicate or "nesosilicate" mineral created from a combination of aluminium and fluorine. It crystallizes in the orthorhombic system and it's crystals are prismatic in form.
Absolute Hardness: 200 ...
In crystals of the tetragonal system each face is an identical isoceles triangle; this variant of the tetrahedron is called a tetragonal tetrahedron. In crystals of the orthorhombic system the faces consist of two pairs of different isoceles ...
Within each of the systems, the cyrstals can mineralize into different crystal habits (form). The seven crystal systems are: cubic systems, tetragonal systems, hexagonal systems, trigonal systems, orthorhombic systems, monoclinic systems, ...
The seven crystal systems are: cubic systems, tetragonal systems, hexagonal systems, trigonal systems, orthorhombic systems, monoclinic systems, and triclinic systems. For more information on crystal systems, click here.
They all crystallize in the orthorhombic system, exhibit good cleavage (although not as good as the members of the calcite group), have a weak double refraction in transparent specimens, ...
 See also: Crystal, Crystals, Mineral, Minerals, Crystal System
  
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