Cut Gemstone

---
name: cut-gemstone
locale: wenyan
source_locale: en
source_commit: 82c77053
fence_basis_commit: 82c77053
translator: "Julius Brussee homage — caveman"
translation_date: "2026-04-19"
description: >
  Cut gemstones using cabochon and faceting techniques. Covers rough
  assessment, orientation for optimal color and yield, dopping, cutting
  angles, and crown/pavilion geometry for standard brilliant cuts. Use when
  you have rough gemstone material to cut into a cabochon or faceted stone,
  planning cutting orientation for optimal colour or optical phenomena,
  setting up a cabbing or faceting machine, or selecting the appropriate
  cutting approach for a given material.
license: MIT
allowed-tools: Read
metadata:
  author: Philipp Thoss
  version: "1.0"
  domain: lapidary
  complexity: advanced
  language: natural
  tags: lapidary, cutting, faceting, cabochon, gemstones
---

# 切寶石

以凸面與刻面之法由原料切寶，含原察、定向、黏、磨、刻面之幾。

## 用時

- 有原寶石材欲切為成凸面或刻面石
- 為色、產、光象劃切向
- 首次設凸面機或刻面機
- 欲知標準亮切之冠與亭角
- 為材擇合切法

## 入

- **必要**：原寶石（已識——參 `identify-gemstone`）
- **必要**：切法決：凸面或刻面
- **必要**：目標形與約尺
- **可選**：含金剛鋸之修鋸
- **可選**：含 80/220/600/1200/3000 目輪之凸面機（為凸面）
- **可選**：含索齒、桅、盤集之刻面機（為刻面）
- **可選**：黏蠟或環氧、黏杆、酒精燈
- **可選**：標準定尺之樣（橢、圓、marquise）

## 法

### 第一步：原察與安察

切前察原料。

```text
Rough Assessment Checklist:
+--------------------+------------------------------------------+
| Factor             | Assessment                               |
+--------------------+------------------------------------------+
| Species            | Identified? (MANDATORY before cutting)   |
|                    | Toxic dust risk? (check below)           |
+--------------------+------------------------------------------+
| Fractures          | Internal fractures that limit yield?     |
|                    | Will the stone break during cutting?     |
+--------------------+------------------------------------------+
| Colour zones       | Where is the best colour concentrated?   |
|                    | Can the cut centre the colour?           |
+--------------------+------------------------------------------+
| Inclusions         | Large inclusions that should be cut away?|
|                    | Silk for star stones? (orient for star)  |
+--------------------+------------------------------------------+
| Size and shape     | What finished shapes fit this rough?     |
|                    | Calibrated size possible?                |
+--------------------+------------------------------------------+
| Yield estimate     | Approximate finished weight as % of rough|
|                    | Typical: 25-40% for faceting             |
|                    | Typical: 40-60% for cabochons            |
+--------------------+------------------------------------------+

SAFETY — TOXIC DUST MATERIALS:
These minerals produce hazardous dust when cut. Use wet cutting ONLY,
ensure ventilation, and wear an appropriate respirator:
- Chrysotile (asbestos serpentine) — NEVER cut dry
- Malachite — copper carbonate dust is toxic
- Cinnabar — mercury sulfide, extremely toxic
- Orpiment/Realgar — arsenic compounds
- Chrysocolla — copper silicate, moderate risk
- Tiger's eye (fibrous) — fine silica fibers

ALL stone cutting produces silica dust. Always use water cooling
and never grind or cut dry without a dust extraction system.
```

1. 確種識（若疑，先運 `identify-gemstone`）
2. 察毒塵險——某材需特防
3. 於強透光察斷裂
4. 映色區與夾之位
5. 估原可產何成形

**得：** 有文之原察，種確、裂映、色區識，切劃已成。

**敗則：** 若原多裂，考可穩否（多孔材以環氧浸）或產是否過低。某原不如售或換為標本。

### 第二步：定向劃

為色與象決最切向。

```text
Orientation Principles by Stone Type:

PLEOCHROIC STONES (tourmaline, sapphire, tanzanite, iolite):
- Orient the table perpendicular to the crystal axis showing
  the best face-up colour
- Tourmaline: the c-axis often shows dark/opaque colour —
  orient the table to view the a/b axis colour
- Sapphire: slight pleochroism — orient for deepest blue face-up
- Tanzanite: trichroic — blue/violet axis preferred for table

STAR STONES (star ruby, star sapphire):
- Silk (rutile needles) must be parallel to the base
- Cut as cabochon with the dome centred over the silk
- The star appears at 90 degrees to the silk orientation

CAT'S EYE STONES (chrysoberyl cat's eye, tiger's eye):
- Fibrous inclusions must run perpendicular to the length
  of an elongated cabochon
- The eye appears as a bright line across the shortest dimension

COLOUR-ZONED MATERIAL (sapphire, ametrine, watermelon tourmaline):
- Position colour zones so they are not visible face-up
- Or feature them intentionally (ametrine, watermelon tourmaline)
```

1. 定石多色否——以二色鏡由多向觀
2. 象石（星、貓眼）識夾式而相向
3. 色區材，決隱或特顯
4. 以鋁筆於原標向
5. 於所擇向劃台位與深以最產

**得：** 標原石示台向、向、約界。切劃優化色顯與產。

**敗則：** 若最色向與最產衝，按優先決：色質幾皆增值甚於克拉。疑則向色。

### 第三步：凸面切

於凸面機形石為凸頂。

```text
Cabochon Cutting Sequence:

EQUIPMENT SETUP:
- Cabbing machine with water drip on all wheels
- Wheel sequence: 80, 220, 600, 1200, 3000 (or 1200 + polish)
- Dop sticks and dop wax (or cyanoacrylate adhesive)
- Safety glasses — MANDATORY
- Avoid loose clothing, tie back long hair

STEP-BY-STEP:
1. SLAB: Cut a slab 5-8mm thick through the best area
2. TEMPLATE: Mark the desired outline (oval, round, etc.)
   using a template and aluminum pencil
3. TRIM: Remove excess material on the trim saw or 80-grit wheel
   Cut close to the line but leave 1-2mm margin
4. DOP: Attach the slab to a dop stick with dop wax
   Heat the wax, press the stone flat-side down, centre it
5. SHAPE (80 grit): Grind to the template outline
   Work all the way around, maintaining symmetry
6. DOME (220 grit): Shape the dome profile
   Standard dome height = ~1/3 of the stone's width
   Keep the dome symmetrical — check from all angles
7. SMOOTH (600 grit): Remove 220-grit scratches
   Work systematically, keeping even pressure
8. PRE-POLISH (1200 grit): Remove 600-grit scratches
   The surface should feel smooth to the fingernail
9. FLAT BOTTOM: Remove the stone from the dop, re-dop
   face-down, and grind the bottom flat on 220 → 600 grit
10. POLISH: See polish-gemstone skill for final finishing
```

1. 設凸面機於諸輪有水流
2. 戴安鏡——無例
3. 切板標樣界
4. 牢黏石——磨時鬆石危
5. 於 80 目磨至形，220 成頂，600 與 1200 平
6. 守頂曲一致——不勻頂拋後顯「平點」

**得：** 均頂凸面石備終拋，界勻、頂高勻、1200 目無餘跡。

**敗則：** 若頂有平點或不對稱，返 220 目重形。寧損微材勿拋不勻頂。若磨時脫黏，慎重黏而繼——先察石無損。

### 第四步：刻面

以刻面機切精幾面。

```text
Standard Round Brilliant Angles (quartz-family, RI ~1.54):
+------------------+-------+--------+
| Facet            | Angle | Index  |
+------------------+-------+--------+
| Crown main       | 42°   | 96-index: 3,9,15,21,27,33,39,45 |
| Crown break      | 25°   | (bisect mains)                   |
| Crown star       | 15°   | (bisect breaks toward table)     |
| Table            | 0°    | flat    |
| Pavilion main    | 43°   | 96-index: 3,9,15,21,27,33,39,45 |
| Pavilion break   | Use GemCad or published diagrams           |
+------------------+-------+--------+

Standard Round Brilliant Angles (corundum, RI ~1.76):
+------------------+-------+
| Facet            | Angle |
+------------------+-------+
| Crown main       | 37°   |
| Pavilion main    | 41°   |
+------------------+-------+

CRITICAL: Pavilion angles determine brilliance.
- Too shallow → light leaks through bottom ("windowing")
- Too steep → dark extinction zones
- Correct angle → total internal reflection (brilliance)
```

1. 擇目形與材 RI 之發刻面圖
2. 備原：平亭側（尖底將向下）
3. 黏石——圓石用錐黏，他用平黏
4. 粗盤（600 目金剛）先以發角切亭面
5. 諸亭面會於精點（「culet meet」）
6. 轉至錐黏（或用轉具）以切冠
7. 切冠主、續破、後星，終立台
8. 每層先拋後拋（盤與膏擇參 `polish-gemstone`）

**得：** 刻面石有精會、勻面、佳對稱、合材 RI 之正角。

**敗則：** 若會偏，角或索設微誤。重察發圖。「追會」（調一面以修他）積誤——大誤宜重切層。小會誤為初學者常而不顯影響亮。

### 第五步：切後察

終拋前察切石。

1. 洗石徹
2. 察對稱：上觀（界）、側（比）、透台（會精）
3. 凸面：驗頂勻、察平點、確界勻
4. 刻面：於 10x 放大察會，察切段餘劃
5. 量終尺與重
6. 若發缺，返宜切步再拋

**得：** 全切石合對稱、會、表備之質準，備拋。

**敗則：** 若發大缺（對稱劣、會敗、比誤），即重切時比拋敗石再切效。記錯為下石

## 驗

- [ ] 切前已識種而察毒塵險
- [ ] 通始終戴安具（眼護、塵濺控）
- [ ] 諸磨切水冷啟
- [ ] 向劃以最色或象
- [ ] 凸面頂對稱無平點（凸面徑）
- [ ] 面會聚於點無偏（刻面徑）
- [ ] 終尺已量記
- [ ] 石無切段劃備拋

## 陷

- **切未識石**：某材產毒塵（孔雀、朱砂、溫石棉）。切前皆識。皆用水冷。
- **略向劃**：切多色石無向以色可生暗或偏色成石，正向則美。
- **乾磨**：乾磨產矽塵（慢性害）而過熱石（熱震可裂）。諸輪盤宜續流水。
- **跳目**：由 220 至 1200 留深劃，拋後顯。每目須全除前目之劃。
- **黏敗**：黏不足致石磨時移或飛。足蠟、石暖（非冷）、黏冷透再磨。

## 參

- `identify-gemstone` — 切前需種識
- `polish-gemstone` — 切後續步，含盤擇、膏擇、終飾