Boron, however, is more easily concentrated (in evaporites). Beryllium is found in pegmatites, which are less common. The estimated resource (not reserve) of Be is 100,000 tons (USGS). This would be enough for ARC reactors supplying just 1% of current world primary energy demand. The estimated world resource of boron is in excess of 1 billion tons.

https://minerals.usgs.gov/minerals/pubs/commodity/beryllium/... https://minerals.usgs.gov/minerals/pubs/commodity/boron/mcs-...

Correction: the deposits are mostly volcanogenic, not pegmatitic. However, they still aren't very common.