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Impact Melt Meteorites & Shock Ratings

Impact Melt Meteorites or Impact Melt Breccias (IMB) have formed from material that was liquefied or partially liquefied from the extreme pressure and heat generated by a large meteorite or asteroid impact in space. When two bodies in space collide with enough force (due to their mass and velocity) they create massive instantaneous pressures. Depending on the pressure it will affect these meteoroids (later to become meteorites) in different ways. More lightly shocked meteorites may just display dark shock veins running through while the Impact Melts will display a melted and deformed matrix. The information below is derived from studies presented by D. Stöffler et al. (1991).

Meteorites are given a shock rating when they are classified. The scale works from 1 (unshocked) right up to 6 (very strongly shocked). These pressures are given values in GPa. 1 GPa is equal to 10,000 bars or in other words about 5,000 times the pressure of a car tyre! Below is a table outlining the Stöffler Shock Rating system.

Shock Rating Description Pressure
S1 / S2 Unshocked Up to 5 GPa
S2 / S3 Weakly Shocked 5 - 10 GPa
S3 / S4 Moderately Shocked 15 - 20 GPa
S4 / S5 Strongly Shocked 30 - 35 GPa
S5 / S6 Very Strongly Shocked 45 - 55 GPa
S6+ Impact Melt 75 - 90 GPa


Copyright © 2004 - Meteorites Australia
Unclassified Saharan Impact Melt - 13.70g Half-Stone

Copyright © 2004 Mike Farmer - www.meteoriteguy.com
NWA 2085 (L-Impact Melt) - 96g Slice

Copyright © 2004 Martin Horejsi
NWA 540 (H6 Impact Melt)

Copyright © 2004 Martin Horejsi
NWA 540 (H6 Impact Melt) - Close-up Image

Copyright © 2004 Photo taken by Iris Langheinrich  of  the Cat Mountain meteorite.  Specimen from R.A. Langheinrich meteorite museum collection - www.nyrockman.com
Cat Mountain (L5 Impact Melt)

Copyright © 2004 Vincent Jacques
Rammya (H5 Impact Melt)


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