Reidite

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

Epitaxial - crystallographic alignment with a precursor mineral,

Reidite is a rare mineral that has been found only in four crater impacts: the Chesapeake Bay Crater in Virginia, Ries Crater in Germany, Xiuyan Crater in China, and Rock Elm Crater in Wisconsin in the United States.

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

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

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.

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Wikipedia