help me to ID this stone

[jelajemi]

please help me to ID this stone I lappepd it very ligthly and it made this kind of white slurry. It measures 7 in. long, 1 1/2 wide, and 3/4 thick. it feels very smooth. before I lapped it looked like it was made out of two stones, like the carborundums but this one feels very very smooth on both sides, it feels like a swaty hone.the thing on the rigth is sand paper Iused to lapped it as you can see the slurry is white