Each piece of stone is different. Each slab of the mountain is different. Each has different mineral content. They make SLABS out of the HIGH END material that comes off of the mountain. They make TILES out of the LOW-END cuts. That means your marbles (both with the same name) may have ENTIRELY different mineral content because they were sourced from VASTLY different areas.

There is a reason these don't match...they are from different areas. If you want a match, you will need to purchase another SLAB (or two...depending on how many square feet you need) and have it cut into tiles. This would not be the best use of resources or money...but it is possible if you insist on having a matching marble on the backsplash.

Personally I would look to use something else on the wall.

Thank you so much for your comments !