how to calculate tourmaline weight

[sushi]

Hello all!

I have just been given a tourmaline as a gift, and I'm trying to work out the weight. Its a strange shape so i can't really work out how to use the online calculators. Its kind of a oval gumdrop shape! like a jumping bean... cabochon.... completely 3d, no facets etc. Like a elongated marble....

Its dimensions are approx 15mm long, and the top and bottom are a 12mm diameter (circle i suppose) again approx....

Any ideas how i work this out? I'm guessing around 15carat... but thats from looking at it.

Many Thanks
sushi xoxo

 

[chrono]

The easiest is to literally weigh it if you have an accurate machine for small things.

 

[sushi]

Its actually in a 18k bead cap setting so I can't actually weigh it, but ill try!

Thanks
Sushi xoxo

 

[chrono]

How far does it extend into the cap? Was it drilled? The painful way to do this is to calculate the mass (circumference, length, width and etc). I'm sure you can find the mathematical formula online.

 

[LD]

You can use this for a rough idea:

http://www.dendritics.com/scales/carat-weight.asp

However it'll only be rough guide.

 

[minousbijoux]

I was going to offer up the specific gravity and some formulas for calculation but I wouldn't know how to guide you at all if its an asymmetrical shape in a bead cap. Your best bet is to weigh it and try to approximate the weight of the gold bead cap.

edited for typo

 

[sushi]

Hello everyone,

thank you for the input. In answer to your questions, it extends all the way into the cap as far as i can see, and yes it is drilled.

I can't use the usual online calculators due to the shape. Upon looking at it a bit more, i think the shape is more like a briolette cabochon if there is such thing?! It definitely isn't pointed inside the cap, but it does taper i think.

I tried using specific gravity x volume etc and i got to 17.65 carat if the shape was consistent, but as i think now it is tapered, i think my first guess might be about right. So i think I'm anywhere between 15-17 carat!

Im going to get it certified, so i think they will have to take it out of the cap when they do, so ill know more then, but can't do that until next week, hence me trying to work it our now.

Any ideas of briolette formulas?
Thank you!

Sushi xoxo

 

[chrono]

So is the back flat like a cabochon of rounded like a briolette?

 

[sushi]

There is no flat part that I can see. I suppose it's more like a teardrop, but the top part I don't think is pointed, I think it is rounded, but I can't see too much as its stuck into the cap... It's all 3d,

Thanks

Xoxo sushi

 

[chrono]

I suppose all you can do is get a guesstimate then. I'd use the same formula as though it is "whole", then multiply by 0.67 to remove the tapered part. Based on your result of 17.6 ct, I'd guess your stone will be closer to the 13 ct mark.

 

[sushi]

Hi chrono,

Great thanks!

Ill keep you posted when I find out what the weight is!

Thanks

Sushi xoxo

 

[LD]

Silly question but why is the carat weight important?

 

[minousbijoux]

Silly question but why is the carat weight important?

I know - I wanted to ask this too. Would you be willing to share a picture for us to see?

 

[chrono]

For fun? Too curious to wait for an official number?