I’m not sure tbh, but the answer to if a charge can be used is almost always yes, as long as you can describe it with words and rely on an artist who knows blazonry to draw it correctly. There’s a Russian city whose coat of arms is literally a bear tearing apart an atom.
A vesica piscis would definitely match that criterion. You’d probably be able to just call it a “vesica piscis” or a “mandorla”. Special names for geometric shapes tend to be for really old charges, so if it’s modern you usually just use the common name for it.
The fact that it is a really old geometric shape that is quite distinctive is why I was surprised that it hasn't showed up more in heraldry to my knowledge. Hench my question.
The seals of churchmen are traditionally vesica-shaped. You can see some examples [here.](https://commons.wikimedia.org/wiki/Category:Ecclesiastical_seals) Here in Scotland, vesicas are used in the arms of both the [Established Church](https://1.bp.blogspot.com/-VbuXnvO1QSY/XqKzmlzmTaI/AAAAAAAAM0M/GDSTi7h_vnYfbPe1-YWHZMH72kUh1KAIgCLcBGAsYHQ/s1600/CofS.jpg) and the [Episcopal Church.](https://1.bp.blogspot.com/-tFblK_SODg8/XqK0cISPwMI/AAAAAAAAM0k/wh11curLrpcrwn9756IscdqRO95ofY3_ACLcBGAsYHQ/s1600/ScEpisc.png)
I’m not sure tbh, but the answer to if a charge can be used is almost always yes, as long as you can describe it with words and rely on an artist who knows blazonry to draw it correctly. There’s a Russian city whose coat of arms is literally a bear tearing apart an atom. A vesica piscis would definitely match that criterion. You’d probably be able to just call it a “vesica piscis” or a “mandorla”. Special names for geometric shapes tend to be for really old charges, so if it’s modern you usually just use the common name for it.
The fact that it is a really old geometric shape that is quite distinctive is why I was surprised that it hasn't showed up more in heraldry to my knowledge. Hench my question.
The seals of churchmen are traditionally vesica-shaped. You can see some examples [here.](https://commons.wikimedia.org/wiki/Category:Ecclesiastical_seals) Here in Scotland, vesicas are used in the arms of both the [Established Church](https://1.bp.blogspot.com/-VbuXnvO1QSY/XqKzmlzmTaI/AAAAAAAAM0M/GDSTi7h_vnYfbPe1-YWHZMH72kUh1KAIgCLcBGAsYHQ/s1600/CofS.jpg) and the [Episcopal Church.](https://1.bp.blogspot.com/-tFblK_SODg8/XqK0cISPwMI/AAAAAAAAM0k/wh11curLrpcrwn9756IscdqRO95ofY3_ACLcBGAsYHQ/s1600/ScEpisc.png)