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My labradorite pendant cracked


#1

After a few months in its new silver pendant setting my oval shaped labradorite has a crack in the middle. I am sure it wasn’t dropped but I can’t understand why this occurred. Any ideas from anybody? Thanks.
Barbara


#2

Barbara, when I was doing lapidary I was taught to grind a slight inward angle around the bottom edge of the stone. If you set the cab in a tight bezel, this will help ease the stone down in. Without the angle if you push a brittle stone down, you can get a crack started that doesn’t show up until later.Donna


#3

OK so I’m not a gemologist so I’m hoping someone here can give me the
straight scoop.
It seems to me that stones with a lot of “Schiller” tend to be pretty
fragile regardless of their Mohs hardness.
OK Gemologists clue me in.
Have fun and make lots of jewelry
-Jo Haemer
www.timothywgreen.com


#4

Hi @jo_haemer. Great question!

I wouldn’t think it has anything to do with the adularescence (sometimes called schiller). The schiller is more of an optical effect than anything else, though it can be exacerbated by the presence of other inclusions. Labradorite is pretty hard (6.5 I think, maybe less), so I think it is less about the hardness and much more about cleavage. It seems there is disagreement across multiple reliable sources about whether the cleavage is perfect in one direction or two, but I’m not sure that matters for our purposes.

Long story short - it’s delicate and it cracks easily (I suspect) because of cleavage, not hardness or adularescence.

Perhaps someone who knows more than me can chime in!


#5

When I was working on it, I didn’t see any obvious signs of cleavage and it looked like one of the best labs I’ve seen. And the crack appeared several months after it was finished. The fit in the bezel was just right. Maybe I can figure out how to post a photo on this new site. Thanks for your suggestions.


#6

I so understand the feelings of a lovely stone failing, dropped or spontaneously. This is what Idid when wanting to preserve what was left.
Removed the stone from the setting, then if possible resized the Bezel, and inlayed a band of the same metal to reconnect the stone, reset it, recreated the piece.
If there was a chip in the side, I formed a piece to hide the chip and enhance the focal. I’m currently wearing a pendant where there is a SS Leaf covering the chip and now an integral part of the pendant.
Yes I made Lemonade.
Hugs
Terrie


#7

It is not unusual to be able to snap a 1/4" thick slab of labradorite into
several pieces with little more hand pressure than it takes to break an
eggshell. It has a pronounced cleavage. That is a function of its
molecular structure. Hence labradorite stones are normally cut quite thick.
Since I prefer to cut my stones to be on the more thin and delicate side
(which, with labradorite, is asking for trouble) I almot invariably doublet
them.

Cheers,
Hans Durstling
Moncton, Canada


#8

I have 100s of pounds of slabs that my father cut in the 1960s. After I preform them, I give them time to crack or do whatever they are going to do before I polish and especially before I set them. I am not a gemologist (I did study Geology in college), but it makes sense to me that when you relieve stresses that have been around a finished stone for millions of years, there might be some additional disruption in the next day or two after you have ripped it out of its very old home. This stone may have been cracked before it was set or all it took was the force of being dropped to crack. If you know that a stone was just cut, let it age for a while before you set it, and make sure to look at it with a loop before you do something permanent with it. I love to cut and polish stones, but I do it knowing that there will be some loss…Rob


#9

Here is the lab pendant before the stone cracked from the top to bottom.