Diamonds from Germany??? Unbelievable - but true! Their origin was the impact of a huge meteorite which formed todays Ries crater in Bavaria, with the city of Nördlingen inside.

The rocks that were hit by the meteorite contained graphite (graphite-bearing gneiss) which was turned into diamonds by the immense pressure (60 GPa) exerted by the impact explosion. These diamonds are microscopic (up to 0.3 mm) and have therefore no value as gemstones. However, there are trillions of them. Their estimated total mass is more than 70,000 tons ;-)
The concentration in rocks reaches max. 0.7 ppm which is 0.7 grams per one ton of rocks.

Impact diamonds occur as pseudo-hexagonal, transparent, and birefringent plates, which reach sizes up to 300 μm. Their color is commonly greenish, but can also be black, gray, yellow, or colorless. [cit. of several articles]

The locality is an abandoned quarry in suevite and impact breccias containing heavily shocked biotite-plagioclase and amphibolite fragments and glass bombs. Hence, the houses in Nördlingen are built from diamonds and impact glass and breccia...

You will need a microscope or a REM to see the diamonds - but they exist! Not really an aesthetical highlight - but an exciting geological sample.