Gemstone Surface Polish Lines vs. Growth Lines

Hello! Im extremely new to the world of gemstones but I’m trying to teach myself how to identify inclusions. Im having a really difficult time being able to tell whether the lines im looking at under the microscope are growth lines or if they’re just from polishing the surface.

Are any of these images displaying growth lines?

Any and all tips on how to spot growth lines would also be greatly appreciated!

p.s. these images were taken by a x60 digital microscope from various rubies and sapphires in my collection.

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Hi Sam,

Welcome to the community! The digital microscope you have takes some very good images!

If you haven’t seen this article; this is a really good source on how to approach viewing a stone using a microscope. The Microscope: A Guide for Gemologists - International Gem Society

The first two images seem to be viewing the internal structure (inclusions).
The third one really does seem like a view of growth patterns. However, without viewing the external of the stone first, it might be difficult to distinguish between surface polish and growth patterns internally.

A good way to view surface features is to use an external light source and angle the stone so you see the light reflected back at you. (As illustrated in the article above) You may have to use a low illumination level, so you don’t blind the camera and wash out any features. Surface polish and scratches will become very visible as you rotate the stone around.

When viewing stones, I will draw a sketch of the table and crown facets. Then take note of any features that can be seen using a loupe or mag-visor. I then place the stone under the microscope and start looking at these. Taking notes on each one.

The last image you posted (red stone with straight lines) looks like surface features at adjoining facet edges. That is a really good image!




@SamR31352 if you dont mind my asking. What microscope do you have?

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Thank you for the insight Troy! and for the article, it was very helpful. At a closer glance now with a loupe I was able to better see which ones are surface inclusions and which ones are growth lines!

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its an Andonstar AD246S-M digital microscope which I bought some time go on Amazon for around $130. What I really like about it is that the pod is detachable/adjustable so that it can also be combined with my polariscope for better viewing of smaller gems.

Okay, thanks.

Hi Sam,
Congrats on using magnification to suss out clues to natural vs synthetic. Short of expensive instruments, it is sometimes the only way! If you’re at the mines or nearby with only a loupe it is also the only way! Did the broker or somebody throw a cleverly massaged syn sapphire into the parcel? Did somebody throw a piece of pink glass into that parcel of morganite (this actually happened to me…and I failed to look closely!)?

While not an expert with the loupe or microscope, let me add to and agree with what Troy said. If you rotate the stone as you are looking, you can often see whether the lines are on the surface or internal. And, yes, as he said, changing the light so that it glances off of facets can show that polishing lines are on the surface, like in your last pic, where they stop at a facet boundary. Growth lines never do that, right…just stop at a cliff? Growth lines in syn sapphire are usually curved, so there’s that along with their three dimensional quality. Also, the wavy, slightly curved nature of the lines in the third pic are telltale of synthetic, I think. There are growth lines in syn corundum and wavy swirl lines in glass.

Two other things you might consider. One is to use less magnification for starters, as inclusions may look different at low mag, like 10 to 20X and be identifiable there without cranking all the way up. If you don’t see something you know is natural, then you can go higher. A second idea is to use immersion fluid. Something like refractol or benzyl benzoate is cheap and relatively non-toxic and will let the polish lines and surface features disappear, while the internal features are on display and seen to move in space as you rotate the stone. Just hold it in tweezers in a small beaker of fluid. If you’re not using a lot of magnification, it helps to use a container which has a clear bottom without lettering, etc. I have a plastic two ounce measuring cup from Wal-Mart I’m going to try out!

Hope this helps and thanks for the info on the microscope. Might get one of these to supplement the venerable, retro Gem-O-Lite I have! -royjohn