Help Identifying Mineral

[mgfranz]

I ran across these ribbons of an unusual mineral on the coast of Laguna California, they are abundant and can be found on the tide pools. They are extremely hard and not brittle, the surrounding rock has been eroded which left this standing proud. The color is a dull yellowish hue and the edges are somewhat sharp, they measure about 1/8"-3/16" thick, any ideas?

 

[mgfranz]

Sounds like an interesting solution, however these veins run for anywhere from 1 meter to over 8 meters long, is this normal? I tried to snap off a portion of the vein to no avail, extremely hard and would not break. maybe with a hammer, but I didn't want to do that without permission.

 

[gsimonel]

I have no idea if this is the case in your example, but often tectonic activity will cause rocks to crack and split. Mineral-rich water flow through these cracks and over millions of years the minerals in the water form crystals and eventually fill the crack with a new substance.

If the new mineral filling the cracks is harder than the surrounding rock, erosion will cause the surrounding rock to erode faster than the material filling the cracks, and whatever is in the cracks will appear to bulge outward.