Online CS pictures (?)

[LittleRed]

As I look online I very often see gems with a “stripe” through them. I was thinking it was an undesirable side-affect of heating, but I see it everywhere and now wonder if it’s just how the camera catches the color. Is it from heating and visible in person, just the camera, or something else? This makes a big difference on how I look at stones.

Thanks!

Notice the “stripe” from the 12 to 6 o’clock position.

 

[chatoyancy]

A lot of tourmalines have more than one color. I personally like them.

 

[LittleRed]

A lot of tourmalines have more than one color. I personally like them.

Oh! So it’s a tourmaline thing. This is good to know. Thanks!

 

[mtsapphirelovingannie]

You posted a round gemstone that is probably just multi colored. However, I’m wondering if you may also be referring to the dark or black line sometimes seen in gems.

Many elongated gemstones, for example ovals or pears, can have what looks like a dark line. This has nothing to do with heating but I believe is an issue with cutting. You can see this in diamonds too; it can look like a black bow-tie.

 

[ExoticGems]

What you are seeing the the dichroic nature of tourmaline, the color of the c axis is leaking into the stone so you see the darker c axis colors on the sides and the A axis's colors down the middle. I believe this was what you are asking about.

 

[chatoyancy]

Oh! So it’s a tourmaline thing. This is good to know. Thanks!

I think it is. There is another characteristic called zoning. That happens in sapphire, amethyst and unheated citrine. Iolite does something wonky too. Zoning affects the saturation of a gem as well as the uniformity of the color. Zoning can be useful though. I was able to confirm what a vendor said about a citrine at a gem show. He said the citrine was untreated and I said i could tell because it had zoning.

 

[ExoticGems]

I think it is. There is another characteristic called zoning. That happens in sapphire, amethyst and unheated citrine. Iolite does something wonky too. Zoning affects the saturation of a gem as well as the uniformity of the color. Zoning can be useful though. I was able to confirm what a vendor said about a citrine at a gem show. He said the citrine was untreated and I said i could tell because it had zoning.

Citrine can still have color zoning when heat treated, you would need to see if inclusions within the stone have expanded.

 

[chatoyancy]

Citrine can still have color zoning when heat treated, you would need to see if inclusions within the stone have expanded.

Really? I did not know that. This zoning was really obvious.

 

[arkieb1]

What you are seeing the the dichroic nature of tourmaline, the color of the c axis is leaking into the stone so you see the darker c axis colors on the sides and the A axis's colors down the middle. I believe this was what you are asking about.

+ 1

 

[PrecisionGem]

I think it is. There is another characteristic called zoning. That happens in sapphire, amethyst and unheated citrine. Iolite does something wonky too. Zoning affects the saturation of a gem as well as the uniformity of the color. Zoning can be useful though. I was able to confirm what a vendor said about a citrine at a gem show. He said the citrine was untreated and I said i could tell because it had zoning.

Color zoning in Citrine doesn’t go away with heating. I think you can safely assume all citrine of strong color has been heated. The really pale yellow material most likely is not heated. There is no cost premium for unheated citrine, the cost is base purely on the color.

 

[chatoyancy]

Color zoning in Citrine doesn’t go away with heating. I think you can safely assume all citrine of strong color has been heated. The really pale yellow material most likely is not heated. There is no cost premium for unheated citrine, the cost is base purely on the color.

Thank you Gene. I’m glad I’ve been corrected by you and ExoticGems, so I don’t make that mistake in the future. If you only go on color then, I just want to get a heated Madeira citrine. I love those!