編者注：本文作者為Guild寶石實(shí)驗(yàn)室寶石學(xué)家郜玉杰。
祖母綠中的“蝴蝶效應(yīng)”
“Gota de Aceite” effect in emerald
近期Guild寶石實(shí)驗(yàn)室（香港）收到一枚待檢測(cè)的戒指。這枚戒指的主石是一顆八邊形的綠色刻面寶石，印記顯示該主石重5.1ct，周?chē)瑫r(shí)鑲嵌有鉆石配石。
Recently Guild Gem Lab (Hong Kong) received a ring for testing. The submitted ring contains an octagonal shape faceted green stone, weighing 5.1ct indicated by the hallmark, with fancy cut diamonds around.
圖1 一枚綠色寶石戒指
Figure 1. a green gemstone ring
這顆綠色寶石（以下簡(jiǎn)稱(chēng)“樣品”）的寶石學(xué)特征與祖母綠相符。在鎢絲燈下顯示艷綠色，透過(guò)濾色鏡可見(jiàn)強(qiáng)紅色，如圖2所示。這樣的顏色變化引起我們的懷疑。盡管天然的祖母綠在CCF下會(huì)變紅，但是一些合成祖母綠在CCF下的紅色更為明顯。
The standard gemological properties of the green stone was consistent with that of emerald. This stone exhibits vivid green color under tungsten lamp and strong red color were seen through Chelsea color filter(CCF) as shown in figure 2. The distinct contraction raised our doubts, as it is known that some synthetic emerald may exhibit strong red color under CCF.
Figure 2. Vivid green color under tungsten lamp(left) and strong red color through CCF(right)
我們將樣品放在寶石顯微鏡下觀察，乍看之下，樣品展示出了比較明顯的“水波紋狀”的生長(zhǎng)結(jié)構(gòu)，如圖3-5。這與水熱法合成祖母綠的特征相似，但并不完全一樣。
A quick glance at this emerald under-microscope reinforced our hypothesis. Viewing perpendicular to the table, “zigzag-like” or “water ripple-like” structures, which were similar to those growth structure in hydrothermal synthetic emerald, were easily observed, as shown in figure 3-5. Similar but not the same.
Figure 3. “water ripple-like” structures
圖 4. “水波紋”結(jié)構(gòu)
Figure 4.“water ripple-like” structures
Figure 5.“water ripple-like” structures
另外，該樣品除了近于腰部有幾處小的裂隙外，其它地方并沒(méi)有看到明顯的包體特征。這樣高的凈度也加強(qiáng)了我們的懷疑。正如我們所知，祖母綠或多或少一般都會(huì)有一些包體。
In addition there were little inclusion within this stone except for several small fractures near the girdle which were not seen by naked eyes, and high clarity caused more doubts in our mind.
盡管我們已經(jīng)表示很懷疑，更準(zhǔn)確的說(shuō)我們幾乎有90%的把握這件樣品是一件合成祖母綠。然而，根據(jù)Guild實(shí)驗(yàn)室內(nèi)部標(biāo)準(zhǔn)的檢測(cè)流程，我們還需進(jìn)行進(jìn)行一步的放大觀察和測(cè)試，以求得100%可靠的結(jié)果。
Suspicious as we were and more precisely speaking we were almost 90% sure that this stone was synthetic, we still have to do more careful and meticulous observation and testing for a 100% sure, following The Guild Standard Testing Procedure.
盡管由于樣品處于鑲嵌的狀態(tài)，我們觀察的方向和條件受到了比較大的限制，但是當(dāng)沿著腰部觀察時(shí)我們?nèi)匀话l(fā)現(xiàn)了一些很有趣的現(xiàn)象。如圖6所示，90倍放大條件下，樣品可見(jiàn)“斑狀”或“粒狀”結(jié)構(gòu)。一些點(diǎn)狀的結(jié)構(gòu)具有明顯的油狀外觀。但是這與外來(lái)的油并不一樣。
In spite of the limitation of observing directions and conditions, for that this emerald was mounted in a ring, we still found something interesting, or mesmerizing to be precise, when viewing near the girdle along the length of the stone. As shown in figure 6, “porphyritic” or “granulous” structures were seen under high magnification 90X. Several spots were apparent with oily appearance.
圖 6. “斑狀”或“粒狀”結(jié)構(gòu)
Figure 6. “porphyritic” or “granulous” structures
進(jìn)一步的放大觀察顯示，這些“點(diǎn)狀”結(jié)構(gòu)具有規(guī)則的輪廓，并顯示不同飽和度的綠色。如圖6-A及圖6-B所示，“點(diǎn)狀”結(jié)構(gòu)的輪廓呈明顯的六邊形，這與綠柱石的結(jié)晶習(xí)性很好的吻合。在B區(qū)域的表面，我們也觀察到了階梯狀的生長(zhǎng)紋，這也揭示了祖母綠的生長(zhǎng)過(guò)程。
A further observation illustrated that the “spots” exhibit regular outlines and green color with different intensity. As shown in figure 6-A and 6-B, these two spot showed distinct hexagonal outlines, which is in good agreement with the crystal habit of beryl, who belongs to hexagonal crystal system. Step-like growth structure were also observed, revealing the growing procedure of this sample.
圖 6-A. 區(qū)域A顯示明顯的六邊形輪廓和飽和的綠色
Figure 6-A, area A shows distinct hexagonal outlines with saturated green color
Figure 6-B, area B also shows distinct hexagonal outlines with saturated green color
樣品的紅外光譜與Guild紅外光譜數(shù)據(jù)庫(kù)對(duì)比結(jié)果證實(shí)，樣品為天然祖母綠，排除了合成品的可能性，如圖7所示。樣品的化學(xué)成分分析結(jié)果與Guild數(shù)十年積累的數(shù)據(jù)庫(kù)對(duì)比顯示，該樣品與哥倫比亞祖母綠的化學(xué)成分含量有很好的吻合性。
Further testing of FTIR spectroscopy and comparison with Guild IR spectra database confirmed that this emerald was natural, as shown in figure 7. Chemical compositions of major and trace elements analyzed by EDXRF with more than 330 spots applied were in good agreement with those of Colombian based on abundant data accumulated over three decades by Mr Charles Carmona.
Figure 7. Infrared Spectra of this emerald
以上整個(gè)觀察結(jié)果，包括樣品的高凈度和“油狀外觀”，與祖母綠商貿(mào)中一個(gè)傳奇性的術(shù)語(yǔ)有很好的吻合性，Gota de Aceite, 源自西班牙語(yǔ)，意思為“油滴”，也有稱(chēng)為“蝴蝶效應(yīng)”。這個(gè)術(shù)語(yǔ)被哥倫比亞的祖母綠商人至少使用了三代人，具有悠久的歷史。目前這種光學(xué)現(xiàn)象只見(jiàn)于哥倫比亞的祖母綠中，包括木佐，La Pita，Coscuez和Penas Blancas礦區(qū)。
The combination of the whole scenes, including the high clarity and oily appearance, were in very good agreement with the legendary term circulating among experienced emerald dealers and seasoned connoisseurs , called “Gota de Aceite” originating from Spanish meaning “a drop of oil”. According to Ronald Ringsrud (2008)，This expression have been used by at least three generations of Colombian emerald dealers. And this optical effect may increase the value of a stone. This phenomena is also called “butterfly wing effect”. So far, such optical effect has only been reportedly found in Colombian emerald from various deposit, including Muzo, La Pita, Coscuez, and Penas Blancas mines.
然而，這個(gè)術(shù)語(yǔ)對(duì)于我們大眾是很陌生的，一方面是因?yàn)檫@種光學(xué)現(xiàn)象十分稀少，另一方面即使有這樣光學(xué)效應(yīng)的祖母綠樣品被送到實(shí)驗(yàn)室檢測(cè)時(shí)，也只有資深的寶石學(xué)和經(jīng)驗(yàn)豐富的商人才有可能發(fā)現(xiàn)。一些這樣品質(zhì)的祖母也很有可以被錯(cuò)誤的認(rèn)為是嚴(yán)重注油的天然祖母綠甚至可能是合成祖母綠。這主要是由于這類(lèi)樣品的高凈度、“水波狀”結(jié)構(gòu)和“油狀”外觀等特征與我們平常的貿(mào)易認(rèn)知有很大的差別。
However, this term is unfamiliar for the public mainly because this phenomena is very rare and even the stone does show such effect only experienced gemologists and seasoned dealers can tell. Some emeralds with such qualities may be mistakingly identified as oiled or even synthetic owing to the wavy structure and very high clarity.
為了更好闡釋這一特殊的光學(xué)現(xiàn)象，我們可以這樣說(shuō)：哥倫比亞祖母綠中的“蝴蝶效應(yīng)”就像是克什米爾藍(lán)寶石中的“天鵝絨效應(yīng)”一樣稀有！
To better elucidate this phenomena, the “Gota de Aceite” effect in Colombian emerald is like velvety effect in Kashmir sapphires.
在拍攝顯微鏡下的觀察結(jié)果是一件比較難和費(fèi)時(shí)的工作。因?yàn)槲覀兪褂孟鄼C(jī)或CCD捕捉到的圖像與人眼直接觀察到的現(xiàn)象是有區(qū)別的。為了更好的重現(xiàn)顯微鏡下的現(xiàn)象，我們會(huì)嘗試在同一位置同一放大倍數(shù)下，微調(diào)焦距后拍攝一系列的照片。之后我們會(huì)使用Photoshop對(duì)圖片進(jìn)行混合圖層，得到最好的效果。尤其是當(dāng)我們拍攝“蝴蝶效應(yīng)”時(shí)，由于樣品的油狀外觀的邊界比較模糊，這項(xiàng)拍攝工作變得更加因難。
To be clear, filming the scene under microscope is relatively a hard and time-consuming task. Because what you have captured using a camera or CCD is different from what you see directly under microscope. To reproduce the scene to the fullest, we have to capture a suit of pictures at various focal distances in identical position, direction and magnification. Afterwards, all the pictures were stacked using Photoshop into one picture to show every possible details.When it comes to “Gota de Aceite” effect, filming task becomes more difficult mainly owing to the oily appearance and blurry outlines.
盡管如此，Guild寶石實(shí)驗(yàn)室的寶石學(xué)家們十分感激當(dāng)今拍攝技術(shù)和社交網(wǎng)絡(luò)的進(jìn)步。這些重大的改變使得我們可以與更廣泛的受眾分享我們對(duì)于寶石學(xué)的熱愛(ài)，共同品鑒大自然給予我們的恩賜！
Guild Gemologists are very great grateful for the advance of filming technology and social network that enable us to share our passion of gemology and to appreciate the beauty blessed by our nature with a very broad audience.
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