Need a better picture. There are some things you can do to help us identify it. Get out a flashlight and determine if it is translucent. It appears to be. See if you can scratch a rock of known hardness like Quartz.
See if it reacts with a weak acid like a drop of murine eye drops or vinegar. Lastly, tell us where you found it geographically speaking, not the beach but the beach in Monterey, California.