Tetragonal
4/m 2/m 2/m (D4h)
Three axes at 90 degrees, two equal (a = b ≠ c, alpha = beta = gamma = 90)
The tetragonal crystal system has three mutually perpendicular axes, two of which are equal in length. Crystals commonly form elongated prisms or bipyramids. Examples include zircon, rutile, cassiterite, and vesuvianite.
The tetragonal crystal system has three mutually perpendicular axes, with two of equal length and one different (a = b ≠ c, all at 90°). This creates crystals with a square cross-section — elongated or compressed cubes. About 7% of known minerals crystallize in this system. Tetragonal symmetry sits between the high symmetry of cubic and the lower symmetry of orthorhombic, producing elegant prismatic crystals with distinctive four-fold symmetry.
Symmetry
Tetragonal crystals have one four-fold rotation axis (the c-axis) and may have additional two-fold axes and mirror planes. The square cross-section (a = b) with a different c-axis length means crystals look the same after 90° rotation around the c-axis but different if rotated around a or b. The system contains 7 crystal classes. Common crystal forms include tetragonal prisms {100} and {110}, dipyramids, and the distinctive square outline visible in cross-section. Many tetragonal minerals form stubby to elongate prismatic crystals with square or octagonal outlines.
주요 광물
Zircon (ZrSiO₄) is the most famous tetragonal mineral — the oldest known material on Earth, with crystals from Western Australia dated at 4.4 billion years. Rutile (TiO₂) forms slender tetragonal prisms that often penetrate quartz crystals as golden needle-like inclusions. Cassiterite (SnO₂), the primary tin ore, forms distinctive twinned tetragonal crystals. Wulfenite (PbMoO₄) is prized by collectors for its thin, square tabular crystals in vivid orange and yellow. Scapolite forms columnar tetragonal crystals and is used as a gemstone in yellow and purple varieties.
광물 (4)
Chalcopyrite
CuFeS2
02 Sulfides and Sulfosalts
Cassiterite
SnO2
04 Oxides and Hydroxides
Rutile
TiO2
04 Oxides and Hydroxides
Zircon
ZrSiO4
09 Silicates