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Formula: BN
Valence: B3+N3-
Nitride of boron
Crystal system: Isometric
Specific gravity: 3.46 calculated
Hardness: 9 to 10
Environments
Qingsongite was approved in 2013 and to date (January 2026) it has been reported only from the type locality.
Localities
The type locality is Orebody 31, Luobusha Mine, Luobusha ophiolite, Qusum County, Shannan Prefecture, Tibet, China.
Qingsongite is the natural analogue of cubic boron nitride, which is widely used as an abrasive under the
name “Borazon.” Qingsongite occurs in a rock fragment less than 1 mm across extracted from
chromitite in the deposit. The qingsongite forms isolated
anhedral single crystals up to 1 micron in size in the marginal zone of the fragment; this zone consists of
45 modal% coesite, 15% kyanite and
~40% amorphous material. Qingsongite is enclosed in kyanite,
coesite or osbornite; other
associated phases include native iron, TiO2 II (a high-pressure
polymorph of rutile),
boron carbide of unknown stoichiometry and amorphous carbon.
Coesite forms prisms several tens of microns long, but is polycrystalline,
and thus interpreted to be pseudomorphic after
stishovite. Associated minerals constrain the estimated pressure to
10 to 15 GPa (100 to 150 kbar) assuming temperature was about 1300oC. The proposed scenario for formation
of qingsongite begins with a pelitic (very fine-grained) rock fragment that was subducted to mid-mantle
depths where crustal boron originally present in
mica or clay combined with
mantle nitrogen and subsequently exhumed by entrainment in chromitite.
The presence of qingsongite has implications for understanding the recycling of crustal material back to the
Earth’s mantle since boron, an essential constituent of qingsongite,
is potentially an ideal tracer of material from Earth’s surface
(AM 99.4.764-772).
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