We found this today in Acton CA USA. Would like to know what it is.
From the photo, your stone is appears to be chalcedony, a form of quartz. This is based on texture and its translucency.
It is possible your stone might be something more unusual given its location but you need to determine hardness and density:
- Guide from www.rocksandminerals.com to its hardness.
[Guide from www.rocksandminerals.com on density
Estimate the stone's density: Does your stone feel lighter, heavier or about the same as a similar sized quartz pebble