Vintage anthracite grey mid century modern vase

Beautiful anthracite grey mid century style bud vase with a yin-yang shape. Heavy piece and very good quality. It feels like it could be carved in stone but the color has worn off on the bottom. There is also a bit of wear inside the vase and a dark spot on the back. Please look closely at 3 last pictures The finish is very smooth and soft No markings organic shape I'm not sure how old this piece is but it is very unique and stylish. can be used as bud vase or as home decor measures 5" tall and 4.5" wide at the base