Unknown fossil from decorative border

[John Mc]

Found this stone among the stones in a decorative border around a relative's yard in NJ. Have no idea where these stones originated. Any thoughts would be helpful. Possible fossil is 3 inches long and 3/4 inch at its widest.

Edited August 18, 2019 by John Mc
duplicate picture removed

[grandpa]

I believe what you have is a mineral in the crevice of that rock of the order of calcite or gypsum (possibly quartz).  An acid test (scratch a small area of the xtal and drop vinegar on that area to see if it fizzes) and a hardness test (search moh's hardness scale - gypsum 1.5-2 hardness, calcite 3 hardness, quartz 7 hardness) should narrow down the possibilities.

[John Mc]

Thanks. When I get the chance I'll do that and report back.