---
title: "Convex: meaning in gemology"
description: "A convex stone has no inward corners: a straight line between any two points inside it stays inside. Most cut stones are convex; a heart, with its notch, is…"
url: https://digitalgemology.com/learn/glossary/convex
image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01
---

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[Glossary](https://digitalgemology.com/learn/glossary) · Cutting and files

# Convex

Also called convex solid

A convex stone has no inward corners: a straight line between any two points inside it stays inside. Most cut stones are convex; a heart, with its notch, is not.

## In more detail

A convex stone is the space on the inner side of every facet plane. That makes it fast to trace. A ray enters at the last plane it crosses and leaves at the first plane it meets.

## How we measure it

Our light tools trace each convex cut as an intersection of half-spaces, one per facet. The census does not score the heart. A file of your own must be convex to within 0.1% of its size, or 0.2% for STEP.

## Related terms

- [Facet](https://digitalgemology.com/learn/glossary/facet): A facet is one flat, polished face of a cut gemstone. Its angle and its direction around the stone decide where it sends light.
- [Watertight](https://digitalgemology.com/learn/glossary/watertight): A watertight model is a closed surface with no holes, so it encloses a solid. In a closed mesh, exactly two triangles share every edge.
- [Light census](https://digitalgemology.com/learn/glossary/light-census): The light census is our ray tracer behind the Cut Performance Wheel, the cut-page scores and the Cut Performance Index. It drops a fixed set of rays on a stone from above and counts where each one leaves.
- [Measure your own stone](https://digitalgemology.com/learn/glossary/measure-your-own-stone): “Measure your own stone” lets three of our tools measure your own cutting file or 3D model. They use the same code and settings as for our cuts.

## Learn more

- [The 3D models](https://digitalgemology.com/about/how-we-measure/3d-models)
- [Your own file](https://digitalgemology.com/about/how-we-measure/your-own-file)
- [Digital Gemology Cut Performance Index](https://digitalgemology.com/learn/cut-performance-index)

[All 328 terms](https://digitalgemology.com/learn/glossary)