Brewsmith
Home brewing moogerfooger
I work for a soils engineering company in Orange County, CA and one of the several jobs we do is landslide repair. At a site last year, I found a vein of gypsum running right through the hillside that we were repairing between some houses. In this case, the gypsum was formed when ancient landslides allowed water, carrying minerals, to seep into the cracks in the soil. Over time the gypsum crystalized into this 1+ inch thick vein. There are also some vertical veins connected to the horizontal one.