Question about a Stone w/a Horsetail

JewelFreak · Mar 8, 2011

Last week when I picked up my watch after cleaning at a local jeweler, I took along a blue spinel to get a baseline B&M setting price for comparison w/online vendors. This guy is very good & very nice; spent a good hour playing around w/his stuff & admiring designs he did for clients. But under his microscope, a horsetail showed up that is not visible at all w/a 10X loupe -- knowing it's there, I can see it vaguely w/my 40X LED loupe. It's a cushion, but for description's sake, the inclusion starts at about 11:00 & extends almost all the way down one side under the crown, kind of equidistant between girdle & edge facet of the table. At one end it comes up near the surface.

This jeweler said anyone who set it would do so "at your risk only." Hard for anyone to evaluate w/out photos, but I'm wondering about setting it. Is it a very iffy proposition with something like that? Was thinking about halo-ing it. Pic of the spinel below, sorry I couldn't get one under the jeweler's microscope. Thanks for your input!

--- Laurie

Michael_E · Mar 8, 2011

The durability during setting and after depends upon what you mean by "horsetail". If this inclusion is a group of silky thread like minerals of a different species than spinel, then it shouldn't pose any problems at all. If it is a fracture or healed fracture which is shaped like a horsetail, then the durability depends upon how far that fracture runs through the stone. You say that it runs under the crown and comes close to the surface, but does it come close to the surface at the edge of the girdle where a prong would come close to it? The location could be critical, if the inclusion is a fracture and it comes close to where a prong will touch the stone. Setting does not impose much stress to the stone when done properly, since the objective is to bend the prong by itself and not use the stone to bend the prong against. Of course it depends on the setter, but if they know it''s there, they can avoid putting stress on it, whatever it's composed of.

JewelFreak · Mar 8, 2011

Thank you, Michael. It does look like strands rather than one fracture. Shows up clearly under a microscope but I really can barely see it w/a 40X loupe & it's not well defined at that. If I didn't know it was there, I wouldn't see it w/a loupe at all -- in fact, didn't, looking at it many times, till I saw it under the scope. It ends, if I remember right, under the crown more toward the table, rather than the girdle edge. That's reassuring news. Many thanks.

--- Laurie