Carat weight

[polecat_ferret]

I am extremely green at all this.  I have found out I love it.  But one problem I have been unable to get a straight answer on is comparitive carat weights.  Carats were original for diamonds and 1 carat is 0.2 gram.  Is that correct?
Now, all gems do not weigh the same due to the chemical make up and atomic weights.  So 1 carat of sapphire does not weigh the same as 1 carat of diamond.  Please tell me I am right?
Now, are there equivalent weight tables?  If so, can someone please direct me in the right direction?
I feel real dumb asking this question but I just need to get my head around it!

[JLB]

G'day Polecat_ferret.  I'm brand new too, but as I understand it a carat of diamonds and a carat of sapphire, or a carat of feathers all weigh a carat.   A carat used to be plant seeds and stuff in the old days but now is as you said, 1 carat = .2gm or 5ct to 1 gram.

Don't confuse with karat, a measure of gold purity, nothing to do with wt.

I usually weigh in grains, which is a whole new kettle of fish.   "They" say 4 grains weighs
200 milligrams, but that is apparantlly an old pearl wt.   "Others" say 1 pearl grain = .25gram,
but *I* say 1ct weighs 3.086 grains.

Anyway, lets wait to hear from that old coot Alf.   

[fossickeract]

As JLB says 1 carat of sapphire weighs the same as 1 carat of diamond or anything else, however because some gems are denser than others a 1 carat sapphire will be smaller about half the size than say 1 carat quartz because its denser. Density Sapphire 4.10  Quartz 2.65
        Ted

[Aussie Sapphire]

The others have it right - a carat is a unit of weight so it will always be 0.2 grams.  What makes gems a different size is specific gravity or density.  In the same way that a kilogram block of gold, steel and aluminium all still weigh a kilogram but will have different sizes because gold is much denser than aluminium.

Therefore 1 carat of sapphire does weigh the same as 1 carat of diamond but will be smaller in dimension.  This is why when you are buying a cut gemstone, it is always better to think of dimension rather than weight as it is much easier to visualise exactly what you are aiming for and most commercially cut stone will be cut to standard sizes/shapes to fit in available settings.

For example, a 6mm round sapphire will usually weigh around 1 carat but depending on cutting style, may be substantially more or less.

There is a handy carat weight online estimator in the List of Links (see top menu under the Gems & Gemmology category) and a less comprehensive list of weight formulae in the Lapidary Info category (left hand menu).

Thanks for joining and please feel free to ask more -we're very happy to help where we can.  If we dont know the answer, we'll all have fun together trying to work it out.

cheers
Leah (admin)

[polecat_ferret]

Thanks for that, I appreciate the answers.  The size difference due to density is probably what I was hung up on.  One thing that I am now confused about is grain to carat conversion.  Being an ex shooter who used to load his own ammunition, I resurrected my old powder scales which weigh in grains.  I weigh the stones on that and convert to carats.  The conversion I have is 1 carat = 3.168 grains.  Is this correct?
Much appreciated.

[moonshadow_dancer]

I am not sure if anyone is interested but this is the url to a small downloadable program I have used for a few years that using your pattern, variety of gemstone and size you can estimate the weight, I have had fairly accurate success with it.

The URL is http://www.jewelcutter.com/gem_estimator/

Take Care
Deb 

[Andrew]

 Great link Deb

[Aussie Sapphire]

I weigh the stones on that and convert to carats.  The conversion I have is 1 carat = 3.168 grains.  Is this correct?

Yes - that looks correct.

You can do quick on-the-fly conversions with google. 

for example, type in "convert 5.5 grains to carats" in the search box at google and it will give you an answer above the search results.

In this example, 5.5 grains equals 1.78 carats. 

Also works for currency conversions.

cheers
Leah

[JLB]

  I weigh the stones on that and convert to carats.  The conversion I have is 1 carat = 3.168 grains.  Is this correct?
Much appreciated.

Polecat_ferret. I have a booklet put out by Fisons chem co. that among other things states Gramme per Litre X 10 (3) gives Parts per Million.

And they reckon gramme to Grain (Av,Ap or Troy,  X 15.43
And                  Grain (etc) to gramme, X by 0.064

So, 3.086 x .064 = .197504 or .20 rounded up, which is what we reckoned a carat was.

[Andrew]

 Great info.
 When it comes down to it there are really only a few methods used today in the Gem/Jewellery trade.
 Troy ounce was the reconised weight used for gem rough,now its grams/kilos:
1 troy ounce = 31.1 grams
1 gram =.03215 troy ounce
Conversion methods:
Carats to Grams x by .2
Grams to Carats x by 5.0

 Good ct and Gram scales are very resonably priced today,the range overcomes the complications of even trying to work out uncommon measures.
Cheers Andrew

[polecat_ferret]

Thanks for that, much appreciated.  I did some reverse mathematics with the aid of a computer converter and then hit the books.  I ended up with the same factor as I started out with.  It is all clear and brilliant cut!(Okay, a bad pun!)
Thanks all.

Peter

[gussyy]

Hi, l find that the easiest way to calculate the carat weight of a gem is to weigh it in grams and halve it e.g - .4 of A gram is 2 carat, 1 gram is 5 carats, 1.2 grms is 6 carat etc. 1 carat = .2 of a gram. Hope this helps.

                                 Cheers Gussyy