The early universe
Was far more compact than it is today. Everything was closer together and stars were popping like popcorn and spewing a wide variety of totally awesome stuff. The stars specific makeup and the dust and planets around it formed a wide variety of materials when it popped - hence all the variation. Trillions of stars have popped since the beginning and the earth has been hit by the resultant wave or drifted through the remnants of a large number of them over time.