Emerald, aquamarine are all gem varieties of beryl. The stuff is massive and usually mined in Pegmatite Quarries. There are no xtls in the massive stuff like say a coticule which has tiny garnets or diamond which has tiny diamond xtls unless you go down to the molecular level of course.

If you go to some of the inactive mines like the Strickland Quarry in Connecticut or the Dixon pegmatites in New Mexico you can pick the stuff up by the truckloads. You will rarely find complete xtls and like the chunk I have you will come across cavities with xtls in them however its not the xtls that do the polishing work its just a very hard rock.