Orthorhombic

2/m 2/m 2/m (D2h)

Three unequal axes at 90 degrees (a ≠ b ≠ c, alpha = beta = gamma = 90)

The orthorhombic crystal system has three mutually perpendicular axes of different lengths. Crystals often form prismatic or tabular shapes. Common minerals include olivine, topaz, aragonite, barite, celestine, and staurolite.

The orthorhombic crystal system has three mutually perpendicular axes, all of different lengths (a ≠ b ≠ c, all at 90°). This creates crystals with a distinctive rectangular symmetry — like a stretched or squashed box. Approximately 22% of known mineral species crystallize in this system, making it one of the most common. The orthorhombic system includes many industrially important minerals and several prized gemstones.

Symmetry

Orthorhombic crystals have three mutually perpendicular two-fold rotation axes and/or three perpendicular mirror planes. The three unequal axes create crystals that look different from each direction but maintain perpendicular geometry. The system contains 3 crystal classes: dipyramidal (most common), pyramidal, and disphenoidal. Common crystal forms include pinacoids (pairs of parallel faces), prisms, and dipyramids. The characteristic 'tablet' or 'bladed' crystal habit of many orthorhombic minerals arises from preferential growth along one or two axes.

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Olivine — the most abundant mineral in Earth's upper mantle — is orthorhombic, forming the green crystals known in gem quality as peridot. Topaz (Mohs 8) forms prismatic crystals prized as gemstones. Aragonite is the orthorhombic polymorph of CaCO₃, forming in biological systems (pearls and seashells) and around hot springs. Barite (BaSO₄) is the principal ore of barium and forms distinctive 'desert rose' crystal clusters. Sulfur crystallizes as orthorhombic bipyramids in volcanic fumaroles. Marcasite, the orthorhombic polymorph of FeS₂, forms distinctive cockscomb crystal aggregates.

แร่ธาตุ (7)

Olivine

(Mg,Fe)2SiO4

09 Silicates

Topaz

Al2SiO4(F,OH)2

09 Silicates

Sulfur

S

01 Native Elements

Barite

BaSO4

07 Sulfates, Chromates, Molybdates, and Tungstates

Aragonite

CaCO3

05 Carbonates and Nitrates

Chrysocolla

(Cu,Al)2H2Si2O5(OH)4 · nH2O

09 Silicates

Celestine

SrSO4

07 Sulfates, Chromates, Molybdates, and Tungstates

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What is the Orthorhombic crystal system?
The orthorhombic crystal system has three mutually perpendicular axes of different lengths. Crystals often form prismatic or tabular shapes. Common minerals include olivine, topaz, aragonite, barite, celestine, and staurolite.
What minerals crystallize in the Orthorhombic system?
There are 7 minerals that crystallize in the Orthorhombic crystal system on MineralFYI.
What symmetry does the Orthorhombic system have?
The Orthorhombic crystal system has 2/m 2/m 2/m (D2h) symmetry.
What are the axes of the Orthorhombic crystal system?
The Orthorhombic system is characterized by Three unequal axes at 90 degrees (a ≠ b ≠ c, alpha = beta = gamma = 90).