Elysian park has turned up oodles of old silver coins to the hardcore turf guys in past years. By now, it's been hammered pretty hard for all the classic 4-start deep-turf-silver signals.
As for your particular target: To be honest with you, it looks like just lead slag from some sort of electrical component (ie.: part of an auto battery insides or something). And the appearance of a Jerusalem cross there seems coincidental.