I have seen black beaches too, but in Iceland. Reynisfjara Beach in the south is something special! At first glance, it even scares you a little with its gloomy beauty. Black grains of sand, huge basalt columns and powerful waves. But I was surprised that even in such cold weather (it was about 5 degrees Celsius) you could meet tourists just walking barefoot on this sand. I think you will be interested in seeing other similar places, there is a good resource -
https://findbestbeach.com/. I just read about beaches in different countries there, and they mention several black beaches in Greece and Hawaii, so there is definitely a choice! I myself want to go to Hawaii someday and see this contrast - the black coast and the azure sea.