From the look of it, I'd guess yes. That ultra matte, oiled look. But Maybe designer can answer for sure.

It looks like a "Barroca" or "Santa Rita" Soapstone

It's hard to tell without a better look. Some solid quartz products are coming out with colors similar to soapstone in matte finishes. Soapstone is unique because it changes over time which just adds to it's beauty.

If this were in New England, I'd be more inclined to say it might be Soapstone...
...but since it lacks any graining, is in Illinois, and has hard inside corners along the front edge (Where a stone would be likely to crack during fabrication/transport) it's more likely to be solid surfacing.

Sorry we didn't have the resources at the time of your question to reply back to you. We hope your project turned out beautifully!

Can you tell me who makes this sink? Beautiful!