Dr Walkden found it in the Bristol countryside several years ago.
No-one was able to identify the strange lump of rock made up of tiny bright green spheres and he kept it in a drawer at work.
However, as more evidence of the dinosaur-killing impact was discovered, Dr Walkden realised his rock was identical.
He said: "I had collected a piece of this strange rock with tiny, bright green spheres. No-one knew what it was so I kept it in a drawer and looked at if every so often.
"Then, as recent details of the dinosaur-killing Mexico impact were being publicised, it became clear the sphere structures were identical - what we had was evidence of a major asteroid impact.
