Beryllium is a chemical element in the periodic table with the symbol Be and the atomic number 4. Uniquely strong and light, beryllium is used to make cell phones, missiles and aircraft. Amazing as it is, it's highly toxic - so don't lick it. Seriously.
Gneiss is a high grade metamorphic rock which has been subjected to higher temperatures and pressures than Schist.
And so, in order to Be Gneiss - while you may look ordinary and grey on the outside - you have been fire tested, can withstand enormous pressure, and should never be licked.
All porcelain mugs are 11oz, microwave and dishwasher safe.