Pink transparent stone it maybe obsidian but my research indicates pink colour is very unusual for obsidian
It’s translucent, all pink, slightly refractive you can read letters through when stone is close to letters but not at a distance of 10cm. Cuts or scratches glass fairly easily. Has no bubbles. Very smooth clean polished texture on the broken surfaces. Found on a field in London.
[Fifty pence coin] shown for scale, 27.3mm in diameter