Diamond vs. Ruby weight

[kev-man]

I had a question about diamond weight vs. ruby weight. My fiancee and I were looking at wedding bands. She really like the style of a band that we saw that alternated diamonds and rubies, but she would want it in all diamonds. The weight of the ring we saw was 1.17 ct in diamonds and .91 ct in rubies (total weight 2.0. At the store they said if they replace the rubies with diamonds the total weight would probably be a little higher since diamonds weigh more than rubies. They had to call their central location to get me a price for what it would cost.

Today I got a call that to make the same ring with all diamonds the total weight would be 1.81 ct. This surprised me since I thought it would have to be more than the 2.08 of the rubies + diamonds. They are looking into the question and will get back to me, but I was wondering if any of the experts here had an opinion on it.

I don''t want to order the ring with 1.81 ct (which is a better price than I was expecting due to the lower weight) and then have it be smaller than what we wanted. Let me say I trust this store and I don''t think they are trying anything shady. The salesperson on the phone was very honest that she didn''t know which should weigh more and she will follow up with questions, but she did know that the price was for the same ring we were looking at and just replacing the rubies with diamonds.

Thanks for the help.

 

[Dee*Jay]

Kev, rubies are "heavier" than diamonds (diamonds have a specific gravity of 3.51 and rubies have a density of *about* 4 [I've seen 3.96 to 4.05]) so a ruby of the same ct weight will be smaller than a diamond of that same ct weight.

Keep in mind also that rubies are generally cut deeper, usually with a thicker girdle, and potentially with a "bulge factor" that diamonds don't have, so you need a higher ct wt of rubies to get the same mm face up size as the diamond.

So, long story short, it seems that what the store is telling you now in terms of the ct weight being less for the diamonds than the rubies makes sense. (But your first paragraph states that they told you the ct wt would probably be a litle higher since diamonds weigh more than rubies, which is not correct.)

 

[kev-man]

Thanks for the response.

I definitely wouldn''t consider the first person who told me that at the store of the diamonds weighing more being an expert. I''m just a little concerned b/c we saw a ring in another store that had a total ct weight of 2.0 and thought it was a little small, so when we thought this ring would come to 2.3-2.5 it sounded perfect. It now sounds like it would come to 1.81 which is even smaller than what we saw in the other store.

I know the setting will make a difference as well in the appearance so I can''t decide (since this ring quoted came in a good deal under budget), if we should have them custom make a ring with the same setting as this one with a total ct weight of about 1.3. Any thoughts on how it would come out custom made if we added .5 ct to the total weight? Should it look identical and just bigger or are people usually wary about custom makings when they haven''t seen it before?

 

[Dee*Jay]

Kev, the custom process is always at least *slightly* scary because you haven''t seen EXACTLY what you''re going to end up with. But that being said, I would think you would be pretty safe having he ring made specifying that you want the stones to be the same mm size as the ones that you like, ct weight aside.

 

[JohnQuixote]

It may help to know that the issue here is cut.Rubies do weigh more, but they're typically cut shallower than diamonds in order to entrap body color. A ruby of the same spread as a diamond typically winds up weighing less because it has less volume. When replacing rubies with diamonds or vice-versa the jeweler’s focus should be on spread.

 

[kev-man]

Unfortunately I don''t have all the info on spread and cut depth of all the stones and I doubt I will be able to get it. The ring is 26 round stones and I''m sure if I got into it all the store would say that the maker of the ring would take care of making the ring with all diamonds (this is not custom as they do it regularly) and that care would be taken to make it look like the same ring with all diamonds.

I''m really on the fence of what I should do. We use this store a lot and I haven''t been able to speak to the owner (who I usually deal with but he is out of town). I will probably need to wait and speak with him.

I''m just concerned to have them replace the rubies with diamonds and end up with the 1.81 total ct weight b/c we felt the 2 ct. weight ring we saw at another store was too small. My fiancee''s engagement ring is quite large and we want the wedding band to be noticeable. I think I''m leaning towards having the ring custom made (with total diamond weight of about 2.3 ct) if they feel they can keep the same look of the ring.

Thanks again for all the help, this really is a great board.