Very nice find Alpinerock, and welcome to RHL. You definitely found a nice vug of crystals in that boulder. Great job getting that home.

It's hard to tell from the picture if it's quartz or calcite crystals. It looks like calcite though. Perhaps you could take a close up of those crystals. We can tell which mineral it is by being able to see the exact shape of those crystals. If you can scratch those crystals easily with a knife it's most likely calcite. Lastly, location would be another great indicator of mineral possibilities.