What can be this?

https://preview.redd.it/luwt2xl7lwke1.png?width=1329&format=png&auto=webp&s=7caddd4a8dd526278d568579446883ce1d51eddd

https://preview.redd.it/ub9a0j1alwke1.png?width=1201&format=png&auto=webp&s=040fcdff4da460d3b01a264769c64713ecb0e6aa

I found this grey crystal line on a rock with chalcopyrite, bornite, elemental copper, and cuprite, what can be that? , I hope you can help me.