Baddeleyite
A variety of Minerals
What is Baddeleyite?
Baddeleyite is a rare zirconium oxide mineral (ZrO2 or zirconia), occurring in a variety of monoclinic prismatic crystal forms. It is transparent to translucent, has high indices of refraction, and ranges from colorless to yellow, green, and dark brown. See etymology below. Baddeleyite is a refractory mineral, with a melting point of 2700 °C. Hafnium is a substituting impurity and may be present in quantities ranging from 0.1 to several percent. It can be found in igneous rocks containing potassium feldspar and plagioclase. Baddeleyite is commonly not found with zircon (ZrSiO4), because it forms in silica-undersaturated rocks, such as mafic rocks. This is because, when silica is free in the system (silica-saturated/oversaturated), zircon is the dominating phase, not baddeleyite. It belongs to the monoclinic-prismatic class, of the P21/c crystal system. It has been used for geochronology.
Optical Properties
- Refractive Index
- 2.13-2.20
- Birefringence
- 0.07
- Pleochroism
- Distinct
- Optical Character
- Biaxial negative
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Key Characteristics
Characteristics of Baddeleyite
Baddeleyite is black in color with a submetallic lustre. It has a 6.5 hardness, and a brownish-white streak. Baddeleyite can also be brown, brownish black, green, and greenish brown. Its streak is white, or brownish white. It has a distinct cleavage along {001} and tends to twin along (100). It belongs to the monoclinic system and is part of the P21/c group.
Formation of Baddeleyite
Baddeleyite was first found in Sri Lanka in 1892. It can be found in numerous terrestrial and extraterrestrial rocks. Some of these terrestrial rocks are carbonatite, kimberlite, alkaline syenite, some rocks of layered mafic intrusions, diabase dikes, gabbroid sills and anorthosite. Some examples of extraterrestrial rocks are tektites, meteorites and lunar basalt. Studies have shown that zircon and baddeleyite can be recovered from some anorthositic rocks in Proterozoic anorthosite complexes. Places where these Proterozoic anorthosite complexes can be found are: the Laramie Anorthosite Complex in Wyoming, the Nain and Grenville provinces of Canada, the Vico Volcanic Complex in Italy, and Minas Gerais and Jacupiranga, São Paulo, Brazil. Baddeleyite forms in igneous rocks low in silica, it can be found in rocks containing potassium feldspar and plagioclase. It has been observed in thin section that baddeleyite forms within plagioclase grains. Associated minerals include ilmenite, zirkelite, apatite, magnetite, perovskite, fluorite, nepheline, pyrochlore and allanite. Because of their refractory nature and stability under diverse conditions, baddeleyite grains, along with zircon, are used for uranium-lead radiometric age determinations.
Composition of Baddeleyite
Baddeleyite belongs to the oxide group, having a composition of ZrO2. Similar minerals belonging to the same group are the rutile group: rutile (TiO2), pyrolusite (MnO2), cassiterite (SnO2), uraninite (UO2) and thorianite (ThO2). Baddeleyite is chemically homogeneous, but it may contain impurities such as Ti, Hf, and Fe. Higher concentrations of Ti and Fe are restricted to mafic-ultramafic rocks.
Quick Facts
Physical Properties
- Color
- Colourless to yellow, green, greenish or reddish brown, brown, iron-black, colourless to brown in transmitted light
- Hardness (Mohs)
- 6.5
- Density
- 5.83 g/cm³
- Streak
- White to brownish white
Chemical Properties
- Chemical Formula
- ZrO2
- Elements
- O, Zr
Also Known As
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