coloured stones ratios

[john smith]

Help please. I have been looking at a spinel. its dimensions are L 9.08 mm W 5.71mm D 3.98mm. I am concerned about the depth. Providing there is no window and no extinction would this be an acceptable depth. I have been unable to find the math to work out the depth as a percentage which I think should normally be 50 - 60 percent

 

[chrono]

It would help to know the shape of the stone, how high the crown is , and pictures tell a lot more than the numbers. Normal depth for coloured stones can range from 60% to 80%, depending on many factors.

 

[john smith]

Help please. I have been looking at a spinel. its dimensions are L 9.08 mm W 5.71mm D 3.98mm. I am concerned about the depth. Providing there is no window and no extinction would this be an acceptable depth. I have been unable to find the math to work out the depth as a percentage which I think should normally be 50 - 60 percent

 

[chrono]

You have not provided:
1. Shape of the stone (rectangular, oval, pear?) The depth calculation will differ for each shape.
2. I would like to see the picture of the stone itself to determine the window, extinction, etc
3. Depth will depend on the crown height, cut design and shape of the stone. Please provide a profile view to determine the crown height vs pavilion height.

 

[john smith]

Chronos reply came to my inbox. The stone is online. The information
says step cut. I am unable to post a picture. My main concern is the depth of the stone

 

[chrono]

There is no magical number. I would need all the information requested to help you determine that.

1. Emerald cut stone?
2. Pics please. You can post it here or share the link.

 

[john smith]

Thank you for trying to help chrono. I am starting to understand how little I know about gemstones. I will work on it. the shape is cushion. i am unable to provide a picture or a link.

 

[chrono]

Did the vendor not provide any pictures?
Please do not buy without at least a picture or video of the stone.

 

[Niel]

Are you trying not to post a picture because you are afraid someone will snatch it up? There's always a concern of that but as gemstones are not like diamonds, there's really no way to tell you if the stone is well cut without seeing it. Do you see a window? Why you look at it sideways, does the area above the girdle look thick and pillowy, normal like a diamond, are very squat and flat?

 

[john smith]

No I am not afraid of theft. I am at present in Thailand. The website is AJS. The site is blocked in Thailand so I am unable to send a picture. The stone as I have said previously is a Spinel step cut cushion . L 9.08. W 5.71. D 3.98 mm. Weight. 1.71ct

 

[PrecisionGem]

You can NOT assess a colored stone by math. You can only assess it by looking at it. For round diamonds the proportions can tell you a lot, but not with colored stones and the thousands of different cuts.