3-Billion Year Old Manufactured Spheroids?

At least 200 have been found, and extracted out of deep rock at the Wonderstone Silver Mine in South Africa, averaging 1-4 inches in dia. and composed of a nickel-steel alloy that doesn't occur naturally.

Some have a thin shell about a quarter inch thick, when broken open are filled with a strange spongy material that disintegrates into dust upon contact with air.

Wierd Spheres