The Science of “Inky Black Jade”: Omphacite Jade Explained by Prof. Michelle Au
Introduction
Often mistaken for ordinary black jade, omphacite jade (commercially called Inky Black Jade or Mò Cuì 墨翠) is a rare gemological phenomenon. Professor Michelle Au‘s groundbreaking study reveals its unique mineral composition—over 90% omphacite—and how to distinguish it from imitations. This guide deciphers her research for collectors and gemologists.
1. Defining Omphacite Jade
1.1 Key Characteristics
- Color:
- Reflected light: Jet black.
- Transmitted light: Deep emerald-green.
- Physics:
- Hardness: 7 (Mohs).
- Density: 3.34–3.44 (higher than jadeite).
- Refractive Index: 1.667–1.670.
- Structure: Micro-fibrous texture (polishes to glassy luster).
1.2 Formation & Rarity
- Found in Myanmar’s alluvial deposits, omphacite jade forms under variable pressure/temperature conditions where jadeite transforms into omphacite.
- <1% of jadeite deposits contain >50% omphacite.
2. Scientific Authentication
2.1 Spectroscopy
- Infrared Peaks:
- Omphacite: 1,040 cm⁻¹ (vs. jadeite’s 985 cm⁻¹).
- Fakes: Absent omphacite signatures.
- Raman Spectroscopy: Confirms omphacite’s Mg-Al-Fe ratios.
2.2 Chemical Composition
- Formula: (Ca₀.₆Na₀.₄)₁.₀(Mg₀.₄Al₀.₃Fe₀.₂)₀.₈(Si₂O₆).
- Color Cause: Trace chromium (Cr³⁺) + organic carbon.
3. Market Insights & Imitations
3.1 Value Factors
- Top Grade: High transparency (>80% light transmission).
- Carving Demand: Popular for Guanyin/Buddha pendants .
3.2 Common Fakes
| Imitation | Density | RI | Red Flag |
|---|---|---|---|
| Black Amphibole | ~3.00 | ~1.62 | Coarse texture |
| Serpentine | ~2.52 | ~1.52 | Waxy luster |
Quick Test: True omphacite jade shows mirror-like reflection on polished surfaces.
4. Collector’s Checklist
- Verify: Demand infrared spectroscopy reports for stones >$5,000.
- Observe: Check green undertones in transmitted light.
- Avoid: “Black jade” with RI <1.66 or granular textures.
Source: Ouyang, Q. et al. (2002). “Mineralogical Study of Omphacite Jade.” Journal of Gems and Gemmology, 4(3), 1–4.
「墨翠」的科學：綠輝石玉權威解析
引言
常被誤認為普通黑玉的綠輝石玉（商業名墨翠或Inky Black Jade），其實是寶石學中的稀有存在。歐陽秋眉教授的研究揭示其礦物組成——90%以上綠輝石，並教您辨別仿品。
1. 綠輝石玉的定義
1.1 關鍵特徵
- 顏色：
- 反射光：墨黑色。
- 透射光：暗綠色。
- 物理性質：
- 硬度：7（莫氏）。
- 密度：3.34–3.44（高於硬玉）。
- 折射率：1.667–1.670。
- 結構：顯微纖維狀（拋光後呈玻璃光澤）。
1.2 形成與稀有性
- 產於緬甸沖積礦床，在高壓變質環境中由硬玉轉化而成。
- <1% 翡翠礦含綠輝石超過50%。
2. 科學鑑定法
2.1 光譜分析
- 紅外光譜峰：
- 綠輝石：1,040 cm⁻¹（硬玉為985 cm⁻¹）。
- 仿品：缺乏特徵峰。
- 拉曼光譜：確認鎂-鋁-鐵比例。
2.2 化學組成
- 化學式：(Ca₀.₆Na₀.₄)₁.₀(Mg₀.₄Al₀.₃Fe₀.₂)₀.₈(Si₂O₆)。
- 致色原因：微量鉻（Cr³⁺）＋有機碳。
3. 市場洞察與仿品
3.1 價值要素
- 頂級品：透明度高（透光率>80%）。
- 雕刻需求：常見觀音/佛像題材（圖版1-4）。
3.2 常見仿品
| 仿品 | 密度 | 折射率 | 破綻 |
|---|---|---|---|
| 黑色角閃石玉 | ~3.00 | ~1.62 | 顆粒粗糙 |
| 蛇紋石玉 | ~2.52 | ~1.52 | 蠟狀光澤 |
簡易檢測：真品拋光面可清晰映出人影。
4. 藏家行動指南
- 驗證：超過5,000美元需附紅外光譜報告。
- 觀察：透光檢查綠色底調。
- 避開：折射率<1.66或顆粒狀結構的「黑玉」。
資料來源：歐陽秋眉等（2002），墨翠——綠輝石玉的礦物學研究，《寶石和寶石學雜誌》，4(3)，1–4。
Read More
Michelle Au: The Gemstone Luminary
- The Symbolic Language of Jadeite: Decoding Auspicious Motifs in Chinese Culture
- Jadeite Texture Types & Their Geological Significance – Prof. Michelle Au’s Structural Analysis
- The Mineral Composition of Jadeite: A Scientific Breakdown by Professor Michelle Au
- Will Jadeite Prices Continue to Rise? – Insights from Professor Michelle Au
- Why Padparadscha Sapphires Lost Their Value: The Heat Treatment Controversy
- Classifying Burmese Jadeite: Mineralogy & Infrared Spectroscopy by Prof. Michelle Au
- Can Myanmar Jade Auctions Predict Retail Prices? Market Realities by Prof. Michelle Au
