Hi stanleychs1437,
There is more about natural rubber and synthetic rubber in post #2 here and there is more about blended Talalay (which is a 70/30 synthetic/natural blend not 60/40) and natural Talalay in post #2 here. Natural and synthetic are both equally “rubber” (they are not polyurethane which is another type of foam completely) and blended Talalay is a very high quality and durable material that if anything is probably a little more durable than natural Talalay in the lower ILD’s. Synthetic rubber is made from a copolymer of styrene and butadiene and both of these are generally sourced from petroleum (although there are also other sources as well) but they are inert and stable when they are copolymerized together and cured.
There is also more about all the different types and blends of latex in post #6 here.
The Talalay latex in your mattress is certainly a very high quality and durable material and I think you made a great choice. Congratulations on your new mattress 
I’m also looking forward to your comments and feedback once you’ve received it.
Phoenix