A quartz sphere is made by grinding rather than casting: the rough is cut roughly round, then rotated between two cup-shaped cutters with progressively finer abrasive until the surface is true. It is a slow job, and the price climbs steeply with diameter because the volume of material removed grows faster than the surface.
Natural clear quartz usually carries some inclusions — a faint veil, a small fracture, a phantom plane — and these are visible inside the finished sphere rather than hidden. The stand is carved beech with a shallow cup; the sphere sits in it rather than being fixed.