Outstanding work. I've had a good many more failures than successes with soapstone.
You probably already know this, but the standard finish for soapstone is many coats of mineral oil and they are normally applied over a long period of time. However, if you combine walnut oil and carnuba they will finish and seal it enough to hold water after only a few coats. Also the lighter green is probably also soapstone that formed in a fracture in the darker green soapstone. Quartz is extremely hard, about 7 on the hardness scale, soapstone is about 1.5-2 hardness; that is greater than the differance between a piece of drywall and a concrete block.