Reidite

Reidite is a very rare mineral created when zircon undergoes high pressure and temperatures. It is commonly associated with meteorite impacts.

Reidite
General
Category	Zircon group
Formula (repeating unit)	ZrSiO4
Strunz classification	9.AD.45
Crystal system	Tetragonal
Crystal class	Dipyramidal (4/m) H-M symbol: (4/m)
Space group	I41/a
Unit cell	a = 4.738, c = 10.506 [Å], Z = 4
Identification
Formula mass	183.31 g/mol
Color	Colorless to white
Crystal habit	Epitaxial - crystallographic alignment with a precursor mineral, occurs as inclusions in other minerals.
Cleavage	None
Fracture	Irregular/uneven
Tenacity	Brittle
Mohs scale hardness	7.5
Luster	Adamantine
Streak	White
Diaphaneity	Translucent
Specific gravity	5.16
Optical properties	Uniaxial (+)
Refractive index	nω=1.64, nε=1.655
Birefringence	0.0150
Pleochroism	None
References	[1][2]

On Earth, reidite has been found only in seven crater impacts: the Chesapeake Bay Crater in Virginia; Ries Crater in Germany; Xiuyan Crater in China; Woodleigh Crater in Western Australia;[3] Rock Elm Crater in Wisconsin;[4] and Dhala Crater in India[5] and Pantasma crater in Nicaragua.

In 2015 an occurrence of reidite was reported from the Precambrian Stac Fada Member structure in North West Scotland, further supporting its impact origin.[6]

Libyan desert glass may show lattice deformation in zircon that is interpreted as evidence of this material having previously contained reidite, and as such constitutes strong evidence for its impact origin.[7]

Name origin

Reidite is named after the scientist who first created the high pressure phase in the laboratory in 1969, Alan F. Reid.

Formation

Zircon morphs into reidite when shock waves from meteorite impacts hike up pressures and temperatures to extreme levels, equal to those deep inside the Earth where diamonds form. The pressure makes minerals tightly repack their molecules into denser crystal structures. Reidite has the same composition as regular zircon but is about 10 percent denser.[4]

Related silica minerals

Relationship of Reidite to Other Specimens

9.AD.25	Uvarovite	Ca3Cr2(SiO4)3
9.AD.25	Wadalite	(Ca,Mg)6(Al,Fe^3+)4((Si,Al)O4)3O4Cl3
9.AD.25	Holtstamite	Ca3(Al,Mn^3+)2(SiO4)2(OH)4
9.AD.25	Kerimasite	Ca3Zr2(SiO4)(Fe^3+O4)2
9.AD.25	Toturite	Ca3Sn2(SiO4)(Fe^3+O4)2
9.AD.25	Momoiite	(Mn^2+,Ca)3V2^3+(SiO4)3
9.AD.25	Eltyubyuite	Ca12Fe10^3+Si4O32Cl6
9.AD.25	Hutcheonite	Ca3Ti2(SiAl2)O12
9.AD.30	Coffinite	(U^4+,Th)(SiO4)1-x(OH)4x
9.AD.30	Hafnon	HfSiO4
9.AD.30	Thorite	(Th,U)SiO4
9.AD.30	Zircon	ZrSiO4
9.AD.30	Stetindite	Ce^4+SiO4
9.AD.35	Huttonite	ThSiO4
9.AD.35	Tombarthite-(Y)	Y4(Si,H4)4O12−x(OH)4+2x
9.AD.40	Eulytine	Bi4(SiO4)3

See also

• Rock Elm Disturbance
• List of minerals

References

1. "Reidite". mindat.org. Hudson Institute of Mineralogy. Retrieved 18 March 2015.
2. "Reidite Mineral Data". Webmineral.com. Retrieved 18 March 2015.
3. Discovery of reidite, one of the rarest minerals on Earth, may reveal Australia's biggest crater ABC News, 16 October 2018. Retrieved 17 October 2018.
4. Oskin, Becky. "Rare Mineral Discovered in Ancient Meteorite Impact Crater". Livescience.com. Livescience. Retrieved 24 March 2015.
5. Li, Shan-Shan; Keerthy, S.; Santosh, M.; Singh, S.P.; Deering, C.D.; Satyanarayanan, M.; Praveen, M.N.; Aneeshkumar, V.; Indu, G.K. (February 2018). "Anatomy of impactites and shocked zircon grains from Dhala reveals Paleoproterozoic meteorite impact in the Archean basement rocks of Central India". Gondwana Research. 54: 81–101. Bibcode:2018GondR..54...81L. doi:10.1016/j.gr.2017.10.006.
6. Reddy, S. M., et al. "Precambrian reidite discovered in shocked zircon from the Stac Fada impactite, Scotland." Geology (2015): G37066-1.
7. Cavosie, Aaron J. "How we solved the mystery of Libyan desert glass". The Conversation. Retrieved 2019-10-12.

External links

• List of Minerals