July 17, 2015 at 2:59 am #198884
I am hoping someone will shed some light on a question I have concerning Thermal Impact damage on Blue-green Sapphire.
I am currently trying to find out if its possible to tell if a Sapphire has been damaged due Thermal Impact or other means?
The stone in question has a Cleve across the stone that apparently is only visible at a certain angle in the correct lighting conditions.
If an expert in the field of gemology has a look at a sapphire with this affliction, is there a 50 50 chance they can tell what the damage to the stone has been caused by?July 24, 2015 at 12:43 am #198997
Hi I am not an expert but the sapphires I have dealt with are all volcanic.
I have had plenty of experience in digging Central Qld (Australia) sapphires and cutting them. These are volcanic and most are broken and very rarely do you get a full crystal. This is because after the volcanic eruptions and the sapphires were sitting in about 15 metres of basalt over 50,000 million years of weathering being covered by sea at least 7 times and being washed and battered around most were broken and indeed have flaws/cracks in the stones. These are sometimes very hard to detect and you may only discover the flaw during the faceting of the gemstone
as far as Thermal goes, I would suspect that in a lot of cases the fractures would be a healed fracture. meaning that it may have been fractured under extreme pressure but then healed again through the thermal process
hope this helpsAugust 1, 2015 at 4:29 pm #199109
An interesting thread. I don’t recall ever seeing a cleavage in a sapphire. Cleavage stated in the books for sapphire is, “None”. I agree with Syd above … more likely a fracture that has fingerprint healed. You do see discoid or halo fractures from heat treatment though. The only other thing that comes to my mind, without seeing the stone of course, would be the possibility of a twinning plane. Would you care to post a photo so we can see what you are seeing?August 13, 2015 at 5:17 am #199193
Areias described it is only visible on certain lightening conditions and directions, its more likely a twinning plane
You must be logged in to reply to topics in this forum.