China Black Marble:(if your stone is older than 10 years you don’t need to worry its not going to be China Black)
This is a extremely soft lower quality low grade marble. We have seen on occasion were dishonest contractors or GM have installed this cheaper marble without the homeowners knowledge. I would only use it on a wall or around a fire place in your Pittsburgh home. For floors it will not stand up to foot traffic and is a nightmare to repair. This stone is very difficult to maintain even water can bring out odd looking features of the stone.
In fact there are only a few people in the USA that can polish this stone at all. The Chinese polish this type of stone with lead which is illegal and unsafe for me to use here in Pittsburgh.
The photo is a china black that we restored. It took about 3-8 hrs per stone to restore so we only touched the ones that were damaged