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[Roger Warin]

Large Shatter Cone in Jurassic limestone from the Steinheim meteorite crater, found next to the central uplift within the town of Steinheim (Germany).
The diameter of this crater is about 3.8 km.
Age: 14.5 million years (synchroneous to the Ries impact).
Shatter Cones are produced when impact shock wave with pressures of about 2 GPa to 30 GPa passes the target rock deep below the point of impact.
Apexes of cones are directed towards the source of the wave.
Roger.

[Mark Ost]

Classic Roger
With a bit of looking at my example you can see what yours shows so well. The convergent lines of deformation. That is a nice classic example.

[Roger Warin]

Hi Mark,
Thank you.
All rocks can give Shatter Cones, but when the texture is fine-grained as limestone, the rock faithfully can be bent by the shock waves.
In addition, other factors are important as impact magnitude, wave reflections, etc.
Note that volcanoes cannot induce such phenomena, or create shocked quartz. These are the features of a meteorite crater.
Roger.

[Mark Ost]

Absolutely. I don't know any volcanic action that can generate that kind of force. Your thin sections are really good also. All the ones I have seen have the linear features in the quartz grains and what seems to be shadows for lack of a better word in thin section. The only thing I ever have seen as far as visual indications of shock is melt glass incorporated into the rock where there would be no volcanic activity to produce the glass. I received a nice piece of Chinese quartz yesterday that has the fracture you so well illustrated. I can understand where a lot of folks would like to find these extraterrestrial rocks as there is a fair amount of interest and a lot of media shows on impact; but in reality I suspect they are far and few between unless you are in the right spot. The best advise is "when you hear hoof beats; think horses not zebras".

[Mark Ost]

I have been to Berringer Crater in Arizona and the craters in Odessa Texas. I also have seen and examined the cores from the Chesapeake Bay Impact Crater, drilled by Dave Powers at the USGS. Of course that one is under quite a bit of sediment and the bay today. The cretaceous bedrock is highly fractured and brecciated in the cores. I forget how far down they had to go, maybe 3000' bgs. The fractures from the crater exert controls on the groundwater in the area and may explain unusual curves in the rivers that feed the bay.