In my visits to garage sales, antique stores, and recycling centers I sometimes find old sewing machine bases. These cast iron bases were made near the turn of the last centry and were one of the first insdustrial products in many homes. This is third sewing machine base I've used. The others were from Sears and White sewing machine company. For a focus stone I used a large slab of agate I got at the Longmont gem and mineral show. The seller told me it was from a quarry in Mexico. To avoid the hastle of importing stone, the seller told me it was smuggeled across the border, hence the name sumugglers' agate.
The sandtone on the top is from quarries north of Boulder near those used to get stones used in the classic University of Colorado buildings.
I have yet one more base in my inventory. If you'd like a pair of these to use as side tables in your home, let me know and I'll put a top on the other base for you.