There are several different types of silver ore in the world depending on the geography.

Some have gray spider-like veins running through the rocks,

while others can be more gray or black in color. Silver can also be found mixed with quartz and ruby crystal formations. Silver and gold are often found together since they exist in the same base ore material.

credit https://www.providentmetals.com/knowledge-center/precious-metals-resources/geology-of-silver.html

The few times I have seen it, though, that is on a small scale, wire sized tendrils in a smaller rock. If that scales up to human sized runners, I have not seen a pic or sample of that.