Opals can be large, especially since the ones used in boro are made in a lab. The issue is that an opal is close to 33 COE, but not, so the larger the opal, the more the chance of it cracking.
Opals can be large, especially since the ones used in boro are made in a lab. The issue is that an opal is close to 33 COE, but not, so the larger the opal, the more the chance of it cracking.