# 💠 Seating Gemstones: Prong and Bezel Settings

## Learning Objectives
By the end of this lesson, you can:
- Build a simple faceted gemstone that fits the real-world scale of your jewelry piece.
- Explain the parts of a stone: table, crown, girdle, pavilion, and culet.
- Model a four-prong seat where the prongs touch the girdle and leave the table visible.
- Model a bezel seat with a correct inner ledge, wall thickness, and a small clearance.
- Check a setting from front, side, and top views so the stone does not float or sink.

## Quick Review
In the earring lesson, you modeled one earring, mirrored it with an empty as the mirror plane, and checked front and back detail. You will use the same habit here: build one clean setting, then check it from more than one view before you duplicate anything.

## Theory

### Meet the stone
A cut gemstone has a flat top called the {{c1::table}}. The upper slope is the crown, the widest edge is the {{c2::girdle}}, and the lower cone is the pavilion. The bottom point is the culet. The girdle is the part the metal holds.

For a beginner setting, you do not need a perfect gemological model. A clean 16-sided placeholder is enough. In Blender, start with a 16-sided cylinder at the girdle, extrude the top inward to make the table, then extrude the bottom down and inward to make the pavilion. Shade it flat so the facets read as cut surfaces, not a smooth ball.

> [!IMPORTANT]
> Model the gemstone as its own object. The metal should touch the stone, not merge into it. This keeps the fit readable and lets you assign a gem material later.

### Prong setting
A prong setting holds the stone with small metal claws. The key detail is the bearing: a shallow notch or shelf cut into each prong at the girdle line. The stone rests on that bearing. The prong tip then leans slightly over the crown to hold the stone.

Use four prongs for a simple round stone, or six for a larger stone. Space them evenly. At beginner scale, a prong about 1.0 mm thick is a practical starting point. Make the bearing shallow, around 0.25 mm deep. If the prongs are too thick, they hide the stone. If they are too thin, they look weak.

### Bezel setting
A bezel is a continuous metal rim around the stone. Build it as a cylinder with wall thickness, then add an inner ledge called the seat. The girdle rests on the seat, and the top rim sits slightly above the girdle. Later, in real metal, that rim is pushed over the stone. In the model, the rim should look close to the stone without cutting through it.

For a beginner piece, a bezel wall of about 0.8 mm is a safe starting point. Leave about 0.1 mm of {{c3::clearance}} inside the bezel so the stone drops in without intersecting the metal. The seat ledge should be wide enough to support the girdle, not so wide that it covers the pavilion.

| Setting | What holds the stone | Best for | Watch out for |
| --- | --- | --- | --- |
| Prong | Metal claws at the girdle | Showing more of the stone | Prongs too thick or not touching |
| Bezel | Continuous metal rim | Protection and clean lines | Wall too thin or stone sunk too low |

## Worked Examples

### Example 1: Four-prong seat for a 6.5 mm round stone
1. Set the stone diameter to 6.5 mm and its total depth to about 3.9 mm.
2. Place the stone so the girdle sits at the height where the metal will hold it.
3. Make four prongs about 1.0 mm thick at 0, 90, 180, and 270 degrees.
4. Cut a bearing notch about 0.25 mm deep at the girdle line.
5. Lean each prong tip slightly over the crown, but keep the table clear.
6. Check in front view: the stone should not float above the bearings. Check in top view: the prongs should look evenly spaced.

### Example 2: Bezel seat for an 8 mm round stone
1. Start with an inside diameter of 8.1 mm, which gives 0.1 mm clearance around an 8 mm stone.
2. Add a wall of 0.8 mm on each side. Outside diameter = 8.1 + 0.8 + 0.8 = 9.7 mm.
3. Add an inner seat ledge around 0.5 mm wide.
4. Set the top rim about 0.3 mm above the girdle.
5. Check in side view: the stone should rest on the seat, not hang below it. Check in top view: the rim should be even all the way around.

## Guided Practice

### Capstone exercise: set your hero stone
Open your capstone file and choose one hero stone for your ring, pendant, or earring pair. You will block one setting, not the whole piece.

```steps
1. Build a 16-sided gemstone placeholder at real scale. Name it Stone_Hero.
2. Place it where the stone should sit in your design. Keep it as a separate object.
3. Choose one setting: four-prong for an open look, or bezel for a protected look.
4. Model the bearing or seat first, then build the metal around it.
5. Check front, side, and top orthographic views.
6. Save a checkpoint render or viewport screenshot for your capstone log.
```

Answer guide: if the stone floats, lower the seat or raise the metal contact. If a prong covers the table, shorten or thin the tip. If the bezel swallows the stone, raise the stone or lower the rim. If the stone intersects the metal, add a small clearance and check again.

## Expert Corner
- Common mistake: modeling the metal first and forcing the stone to fit. Build the stone first, then make the seat match it.
- Rule of thumb: the bearing touches the girdle, and the prong tip only leans over the crown. The table stays open.
- Common mistake: checking only in perspective view. Use orthographic front, side, and top views for fit.
- Rule of thumb: a bezel wall under about 0.6 mm can look fragile at beginner scale. Start near 0.8 mm.
- Keep the stone and metal as separate objects. This will make the next lesson on shaders much easier.

## Summary & Next Steps
You now know how a stone is held: the girdle sits on a bearing in a prong setting, or on an inner seat inside a bezel. You can build a simple faceted stone, place it at real scale, and check that the metal touches it without floating, sinking, or covering the table.

Review deck:

```flashcard
[
  { "front": "What is the girdle of a gemstone?", "back": "The widest edge around the stone, where the metal usually holds it." },
  { "front": "What is the table?", "back": "The flat top facet of the stone." },
  { "front": "What is the pavilion?", "back": "The lower cone-shaped part below the girdle." },
  { "front": "What is a prong bearing?", "back": "A shallow notch or shelf at the girdle that supports the stone." },
  { "front": "How many prongs are common for a simple round stone?", "back": "Four or six, spaced evenly around the girdle." },
  { "front": "What is a bezel setting?", "back": "A continuous metal rim around the stone, resting on an inner seat." },
  { "front": "Why leave clearance inside a bezel?", "back": "So the stone drops in without intersecting the metal." },
  { "front": "Why model the stone as a separate object?", "back": "It keeps the fit clear and makes material assignment easier." },
  { "front": "What should a prong tip never cover?", "back": "The table or too much of the crown facets." },
  { "front": "Which views should you use to check a setting?", "back": "Orthographic front, side, and top views." },
  { "front": "What does a floating stone mean?", "back": "The stone is not touching its bearing or seat." },
  { "front": "What is a safe beginner bezel wall thickness?", "back": "About 0.8 mm, with a small inner clearance." }
]
```

In the next lesson, you will turn these grey forms into gold and silver, give the stone a believable gem material, and light the piece in a studio setup for a portfolio render.