They exist as deep subsurface veins of ore deposits, but on the surface, gypsum and pyrite and the like typically present as individual crystals in a matrix of feldspars or grossular quartz. Besides silicate rocks, carbonates are the only ones off the top of my head that you can find in ...
which was conducted in the R package adegenet (v. 2.1.5)52. Secondly, individual ancestry coefficients were estimated with sparse non-negative matrix factorization (sNMF) implemented on the R package LEA (v. 3.6.0)53, where