The 4Cs Decoded: Understanding China’s National Diamond Grading Standard (GB/T 16554)
4C標準解密：深入理解中國國家鑽石分級標準 (GB/T 16554)
A Collector’s Guide to China’s National Diamond Grading Standard
For enthusiasts and collectors navigating the world of fine jewelry and东方艺术品 (dōngfāng yìshùpǐn), understanding how diamonds are officially evaluated is paramount. In China, this is governed by the National Standard GB/T 16554 – Diamond Grading. This isn’t just a technical manual; it’s the authoritative framework that ensures consistency, transparency, and confidence in the market. Whether you’re considering a diamond investment or appreciating a piece of镶嵌钻石 (xiāngqiàn zuànshí) jewelry, this guide to the Chinese 4C system will empower your decisions.
藏家指南：中國國家鑽石分級標準詳解
對於探索高級珠寶和東方藝術品世界的愛好者與收藏家而言，理解鑽石如何被官方評估至關重要。在中國，這由 國家標準 GB/T 16554 – 鑽石分級 所規範。這不僅是一本技術手冊，更是確保市場一致性、透明度和信心的權威框架。無論您是在考慮鑽石投資，還是鑑賞一件鑲嵌鑽石珠寶，這份關於中國4C系統的指南都將助您做出明智決策。
Scope and Applicability: What Diamonds Are Graded?
The standard applies specifically to natural, polished diamonds (both loose and set), but with precise conditions:
- Minimum Weight: Loose diamonds must be ≥ 0.04g (0.20 carats). Set diamonds must be between 0.04g (0.20ct) and 0.20g (1.00ct).
- Color Range: It covers the classic colorless to near-colorless range, specifically diamonds in the “colorless to light yellow (brown, gray) series.”
- Cut Style: The primary cut evaluated is the standard round brilliant cut (with 57 or 58 facets).
- Treatment: Diamonds that have undergone treatments like coating or fracture filling are not graded under this standard, ensuring evaluations are for natural characteristics.
Smaller diamonds (<0.20ct) may be graded by reference, but the full, rigorous process is reserved for stones meeting the above criteria.
範圍與適用性：哪些鑽石可以被分級？
該標準專門適用於 天然的拋光鑽石（包括裸石與鑲嵌鑽石），但有精確的條件限制：
- 最低重量： 裸鑽必須 ≥ 0.04克 (0.20克拉)。鑲嵌鑽石必須在0.04克 (0.20克拉) 至0.20克 (1.00克拉) 之間。
- 顏色範圍： 涵蓋經典的 無色至近無色範圍，特指「無色至淺黃（褐、灰）色系列」的鑽石。
- 切工款式： 主要評估的切工是 標準圓鑽型切工（具有57或58個刻面）。
- 處理： 經過如覆膜、裂隙充填等處理的鑽石 不在此標準下進行分級，確保評估的是天然特徵。
更小的鑽石（<0.20克拉）可參照分級，但完整、嚴格的流程僅適用於符合上述條件的鑽石。
The Foundation: The 4Cs (顏色, 淨度, 切工, 質量)
The Chinese standard, like its global counterparts, is built on the 4Cs: Color (顏色), Clarity (淨度), Cut (切工), and Carat Weight (質量). However, it defines specific methodologies and terminologies within a national context.
基礎：4C標準（顏色、淨度、切工、質量）
與國際標準一樣，中國標準建立在 4C：顏色、淨度、切工和克拉重量 之上。然而，它在國家層面內定義了具體的方法和術語。
1. Color Grading (顏色分級)
Color is assessed by comparing the diamond to a master set of calibrated 比色石 (comparison stones) under controlled lighting (a 比色燈 with a color temperature of 5500-7200K) against a neutral white background.
- Grading Scale: The standard uses the D-to-Z scale, with D representing the highest grade of colorlessness. The scale comprises 12 continuous grades: D, E, F, G, H, I, J, K, L, M, N, and <N.
- Fluorescence (熒光強度): The diamond’s reaction to long-wave ultraviolet light is also graded as None (無), Weak (弱), Medium (中), or Strong (強), using a set of master stones for comparison.
Key Takeaway: A diamond’s color grade (e.g., “F-G” on a Chinese lab report for a set diamond) is determined through a meticulous visual comparison process by multiple trained technicians.
1. 顏色分級
顏色的評估是通過在受控光源下（色溫在5500-7200K範圍內的比色燈），將鑽石與一套校準過的比色石在白色中性背景上進行比較。
- 分級尺度： 該標準使用 D至Z尺度，D代表最高的無色等級。該尺度包含12個連續級別：D、E、F、G、H、I、J、K、L、M、N 和 <N。
- 熒光： 鑽石在長波紫外光下的反應也被分級為 無、弱、中、或強，使用一套比對樣品進行比較。
關鍵要點： 鑽石的顏色級別（例如，中國實驗室報告上對鑲嵌鑽石標註的「F-G」）是經過多名訓練有素的技術人員通過嚴謹的視覺比對流程確定的。
2. Clarity Grading (淨度分級)
Clarity evaluates the natural internal and external characteristics (inclusions and blemishes) of a diamond under 10x magnification.
- Grading Scale: The standard uses the following clarity grades, from finest to included:
- LC (Loupe Clean / 無瑕級): No internal or external characteristics visible at 10x magnification.
- VVS1, VVS2 (極輕微內含級): Minute inclusions that are extremely difficult (VVS1) or very difficult (VVS2) to see at 10x.
- VS1, VS2 (輕微內含級): Minor inclusions that are difficult (VS1) or somewhat easy (VS2) to see at 10x.
- SI1, SI2 (微內含級): Noticeable inclusions that are easy to see at 10x.
- P1, P2, P3 (內含級): Inclusions that are visible to the naked eye (from obvious to very obvious).
Key Takeaway: The clarity grade on a Chinese certificate tells you how visible the diamond’s natural birthmarks are under professional, standardized observation.
2. 淨度分級
淨度評估鑽石在 10倍放大鏡 下觀察時的天然內外部特徵（內含物和瑕疵）。
- 分級尺度： 標準使用以下淨度級別，從最優到最差：
- LC (放大鏡下無瑕級)： 在10倍放大鏡下不可見內外部特徵。
- VVS1, VVS2 (極輕微內含級)： 在10倍放大鏡下極難 (VVS1) 或很難 (VVS2) 觀察到的微小內含物。
- VS1, VS2 (輕微內含級)： 在10倍放大鏡下難以 (VS1) 或比較容易 (VS2) 觀察到的細小內含物。
- SI1, SI2 (微內含級)： 在10倍放大鏡下容易觀察到的明顯內含物。
- P1, P2, P3 (內含級)： 肉眼可見的內含物（從明顯到極明顯）。
關鍵要點： 中國證書上的淨度級別告訴您，在專業、標準化的觀察下，鑽石的天然「胎記」有多明顯。
(Continued from previous message)
3. Cut Grading (切工分級)
For standard round brilliant diamonds, cut is evaluated based on two main aspects: Proportion (比率) and Finish (修飾度).
- Proportion (比率): This refers to the precise mathematical relationships between the diamond’s dimensions. Key measurements include:
- Table Percentage (台寬比): Width of the table facet relative to the diamond’s diameter.
- Crown Height (冠高比) & Pavilion Depth (亭深比): The height of the top and bottom sections.
- Girdle Thickness (腰厚比): Thickness of the diamond’s widest perimeter.
- Total Depth (全深比): Overall height relative to diameter.
- Crown Angle (冠角) & Pavilion Angle (亭角): The angles of the top and bottom facets.
- Finish (修飾度): This assesses the quality of the diamond’s polish and the precision of its facet arrangement (symmetry). It looks for issues like抛光纹 (polish lines), an out-of-round girdle, or misaligned facets.
- Grading: Both Proportion and Finish are graded on a three-tier scale: Excellent (很好), Good (好), and Fair (一般). The overall cut grade is determined by the lowest of these two ratings.
Key Takeaway: A Chinese cut grade doesn’t just say “good cut.” It provides a structured analysis of the diamond’s geometry and craftsmanship, which directly influences its brilliance and fire.
3. 切工分級
對於標準圓鑽型鑽石，切工是根據兩個主要方面來評估的：比率 和 修飾度。
- 比率： 這指的是鑽石尺寸之間精確的數學關係。關鍵測量包括：
- 台寬比： 台面寬度相對於鑽石直徑的百分比。
- 冠高比 和 亭深比： 頂部和底部部分的高度。
- 腰厚比： 鑽石最寬周邊的厚度。
- 全深比： 總高度相對於直徑的百分比。
- 冠角 和 亭角： 頂部和底部刻面的角度。
- 修飾度： 這評估鑽石的拋光質量和刻面排列的精度（對稱性）。它關注如抛光紋、腰圍不圓或刻面未對齊等問題。
- 分級： 比率和修飾度均採用三級制分級：很好、好、一般。整體切工級別由這兩項評級中 較低者 決定。
關鍵要點： 中國的切工等級不僅僅是說「切工好」。它提供了對鑽石幾何結構和工藝的結構化分析，這直接影響其閃耀度和火彩。
4. Carat Weight (質量)
This is the most straightforward measurement. Weight is measured in grams (g) with an accuracy of 0.0001g. The traditional carat (ct) is also used in trade, with the conversion 1.00g = 5.00ct. The weight must be stated on the certificate, e.g., 0.40g (2.00ct).
Key Takeaway: Precision is key. The weight on a Chinese grading certificate is a highly accurate measurement, not an approximation.
4. 克拉重量
這是最直接的測量。重量以 克 為單位測量，精確至0.0001克。傳統的 克拉 也在貿易中使用，換算為1.00克 = 5.00克拉。重量必須在證書上標明，例如 0.40g (2.00ct)。
關鍵要點： 精確性是關鍵。中國分級證書上的重量是高度精確的測量，而非近似值。
The Grading Certificate (鑽石分級證書): Your Proof of Quality
A formal Diamond Grading Certificate issued by an accredited laboratory (like the National Gemstone Testing Center, NGTC) is the tangible output of this standard. It is the diamond’s “passport,” containing:
- Certificate Number & Date
- Precise Measurements: Dimensions (max/min diameter, depth).
- The 4C Grades: Final ratings for Color, Clarity, Cut (with proportion details), and Carat Weight.
- Fluorescence Grade
- Clarity Plot: A diagram showing the location of inclusions.
- Security Features: Official stamps and signatures.
For set diamonds, grading is slightly adapted (e.g., color grades are grouped into broader ranges like D-E, F-G, etc., due to the influence of the metal setting), but the core principles remain.
分級證書：品質的證明
由認可實驗室（如國家珠寶玉石質量監督檢驗中心，NGTC）出具的正式 鑽石分級證書 是此標準的具體體現。它是鑽石的「護照」，包含：
- 證書編號和日期
- 精確尺寸： 最大/最小直徑、全深。
- 4C等級： 顏色、淨度、切工（含比率細節）和克拉重量的最終評級。
- 熒光等級
- 淨度素描圖： 顯示內含物位置的示意圖。
- 防偽特徵： 官方印章和簽名。
對於 鑲嵌鑽石，分級會稍作調整（例如，由於金屬鑲托的影響，顏色級別會歸入更寬的範圍，如D-E、F-G等），但核心原則保持不變。
Why This Matters for Collectors on Virtucasa
Understanding GB/T 16554 is not about memorizing technical details. It’s about empowerment:
- Verification: You can confidently interpret Chinese lab certificates, verifying the claims made about a diamond’s quality.
- Informed Comparison: It allows you to compare diamonds graded under the Chinese system with those graded under GIA or other systems, understanding the nuanced differences in criteria.
- Value Assessment: A thorough grasp of the 4Cs as defined in the national standard helps you assess a diamond’s true market value and collectible merit.
- Trust Building: Purchasing diamonds with accompanying national standard grading certificates from reputable labs ensures transparency and reduces risk.
This standard represents China’s commitment to aligning with international best practices while providing a robust, localized framework for quality assurance. For the discerning collector of东方首飾 (dōngfāng shǒushì), it is an indispensable tool for building a meaningful and valuable collection.
這對Virtucasa上的收藏家為何重要
理解GB/T 16554並非關於記憶技術細節，而是關於 賦能：
- 驗證： 您可以自信地解讀中國實驗室證書，驗證關於鑽石品質的聲明。
- 知情比較： 它使您能夠將按中國系統分級的鑽石與按GIA或其他系統分級的鑽石進行比較，理解標準間的細微差異。
- 價值評估： 全面掌握國家標準定義的4C有助於您評估鑽石的真實市場價值和收藏價值。
- 建立信任： 購買附帶來自信譽良好的實驗室的國家標準分級證書的鑽石，可確保透明度並降低風險。
此標準代表了中國在與國際最佳實踐接軌的同時，為質量保證提供了一個強健的本土化框架。對於眼光獨到的東方首飾收藏家而言，它是建立一個有意義且有價值收藏的不可或缺的工具。
