雙語閱讀：黃金和鑽石哪個更稀少？

黃金和鑽石哪個更稀少？

翻譯：塗博士

鑽石代表著永恆，黃金代表著珍貴，兩個都是好東西，但哪個更稀有呢？稀缺度與我們在珠寶店看到的價格有關係嗎？

事實證明，答案並不像你可能想象的那樣“清晰”。

麻省理工學院的地球科學家兼教授烏爾裡希·福爾（Ulrich Faul）說，地球上稀有元素之一的金子作為一種重金屬，是在中子星碰撞過程中形成的。

加拿大新斯科舍省哈利法克斯的達爾豪西大學地球科學教授兼實驗高壓地質研究實驗室副主任亞娜·費託喬克（Yana Fedortchouk）說，在地球形成過程中，由於萬有引力的作用，最重的元素被吸引到了地球的核心，這也意味著在地殼附近很難找到大量的黃金。

雖然密度很低，但你還是可以在地表上找到金子。 費託喬克（Fedortchouk）告訴《Live Science》，金子存在於地殼中各種各樣的岩石中。 “但是要形成礦床，金子的含量必須達到一定的密度才有開採價值。”

根據費託喬克（Fedortchouk）的說法，地殼中金子的平均密度“非常非常低”，為十億分之四。她說，如果要具備有開採價值的黃金密度，金礦的金子儲量必須要高出1250倍。

另一方面，鑽石是由一種非常常見的碳元素在高壓下形成的形態。沒有經歷過高壓的碳元素的形態被稱為石墨，也就是我們鉛筆中的東西。根據《地殼中的流體：它們在變質，構造和化學傳輸過程中的意義》（Elsevier Science Ltd.，1978）一書中的研究，與金相比，地殼中碳的平均密度約為十億分之二十。這本書由著名地質學家威廉·費菲（William Fyfe）撰寫，他已於2013年去世。

因此，鑽石的稀有性與其元素組成無關。不過，大自然將碳轉化為可開採的鑽石礦床的過程是一個極其艱鉅而且極少成功的過程。

費託喬克（Fedortchouk）說：“鑽石只能在地幔（地幔是地殼下面的地球層。）中產生，並以某種方式被帶到地表。另外隕石撞擊時也會形成鑽石，但這些鑽石很小，成不了寶石，沒有什麼價值。在地球地幔深處形成的鑽石可以由深部岩漿帶到地表，也可以是在造山過程中隨著深層岩石的緩慢抬升過程中被帶到地表。但是在深層岩石的緩慢抬升過程中，鑽石會石墨化（變成石墨），到了地表就不再是寶石了。”

形成鑽石所需的條件取決於深度，溫度和壓力：碳被埋在地球表面以下至少93英里（150公里）處，在每平方英寸約725,000磅的壓力（50億帕斯卡）下加熱到約2200華氏度（1,204攝氏度），然後通過火山噴發快速地帶到地表層冷卻下來。 費託喬克（Fedortchouk）說這一非同尋常的過程使天然可開採的鑽石比金礦要更稀少。

但是，福爾（Faul）告訴《生命科學》，在元素成分上，黃金遠比鑽石要稀少。畢竟，碳是地球上最豐富的元素之一，尤其是與金等重金屬相比，而鑽石只不過是碳在極高的壓力下形成的一種形態。

合成鑽石的發明使這個問題（鑽石和黃金哪個更稀缺）更復雜了。科學家可以在實驗室中重現將石墨轉變成鑽石的必要條件（無需火山爆發），但對於黃金卻做不到（遺憾的是，鍊金術仍然是一門偽科學）。根據鑽石設計師（Ritani）的說法，即使合成鑽石與天然鑽石是由相同的物質組成的，但合成鑽石在市場上的售價通常會低30％，因為它們不被認為具有和天然鑽石同樣的價值。

但是，僅僅存在實驗室創造的鑽石這個事實，是否會使鑽石的存在比我們想象的更普遍呢？福爾（Faul）認為確實是這樣的：“首先，一定尺寸以下的鑽石不值得開採，誰會想購買需要放大鏡才能看到的鑽石呢？地表上的黃金比大鑽石要多，但是鑽石作為一類材料並不是特別稀有。我認為，鑽石的名聲有部分與商家非常成功的公關宣傳有關！ ”

本文章最初發表在《生命科學》上。

在開始閱讀英文原文之前，請先複習下列核心詞彙：

rare - adj. 稀少的

gold - n. 黃金

diamond - n. 鑽石

forever - adv. 永遠，長久地

precious - adj. 寶貴的，貴重的

jewelry - n. 珠寶飾物

clear-cut - adj. 明確的，清晰的

turn out - 結果是

heavy metal - 重金屬

neutron - n. 中子

element - n. 元素

formation - n. 形成，組成

gravitate - v. 被吸引到

crust - n. 山頂

concentration - n. 集中，聚集

present - v. 把...交給，提出

deposit - n. 存款，沉澱物，礦床

feasible - adj. 可行的

pressurize - v. 加壓力

carbon - n. 碳

graphite - n. 石墨

lab - n. 實驗室

transform - v. 使改變形態

alchemy - n. 鍊金術

volcanic - adj. 火山的

eruption - n. 爆發

magnify - v. 放大

在複習了以上詞彙後，請將下面的英文原文一口氣讀完，不要在中途停下來去查那些不認識的單詞。有了上面的核心單詞打底，你完全可以將整篇文章讀完並且理解裡面的大致意思。記住，你只要做到大致明白就可以了。

閱讀能力和閱讀量成正比，要提高閱讀量，必須是大量的泛讀，如果要對每個不懂的單詞都去查字典，那麼就不可能通過大量的泛讀來提高你的閱讀量。

這篇英語原文是《塗博士雅思輔導課》直播班上用來訓練學員快速閱讀的文章之一。能夠快速閱讀各個領域的原版文章並找出文中的核心內容，是真正學好英語的最最基礎的技能之一，另一個最最基礎的技能就是聽得懂原版的廣播。有了這兩個最最基礎的技能打底，學員就可以利用好網上大量的原版英語文章和聽力資源，不出國就可以把自己沉浸在英語的環境當中。在建立起強大的語感之後，口語和寫作能力都會自然成長起來。

如果你對某篇泛讀文章特別喜歡，可以在泛讀一遍以後再慢慢地精讀。如果在精讀的過程中對某些句子不是太明白需要講解，或者你希望以後多看到哪方面的雙語閱讀，請直接聯繫塗博士。

Which Is Rarer: Gold or Diamonds?

By Joanna Fantozzi

Live Science Contributor

Diamonds are forever, and gold is precious, but which is rarer? And does that rarity have anything to do with the price we see at a jewelry store?

The answer, it turns out, isn't as "clear-cut" as you might think.

Gold — a heavy metal — is one of Earth's rarer elements, formed in the collisions of neutron stars, said Ulrich Faul, an Earth scientist and professor at the Massachusetts Institute of Technology.

Then, during the formation of Earth, the heaviest elements gravitated toward Earth's core, said Yana Fedortchouk, an Earth sciences professor and co-director of the Experimental High-Pressure Geological Research Laboratory at Dalhousie University in Halifax, in the Canadian province of Nova Scotia. That means that up near the Earth's crust, large amounts of gold are hard to find.

You can find it, though, in low concentrations. It's "present in a large variety of rocks in the crust," Fedortchouk told Live Science. "But in order to form a deposit, it needs to reach certain concentrations to make mining economically feasible."

According to Fedortchouk, the average concentration of gold in Earth's crust is "very, very low," at 4 parts per billion. In order to produce any minable concentration of gold that could be of market value, the gold deposit would have to be 1,250 times more concentrated, she said.

Diamonds, on the other hand, are a highly pressurized form of a very common element: carbon. In its non-pressurized form, it's known as graphite — the stuff in pencils. Compared with gold, the average concentration of carbon in Earth's crust is approximately 200,000 parts per billion, according to "Fluids in the Earth's Crust: Their Significance in Metamorphic, Tectonic, and Chemical Transport Processes" (Elsevier Science Ltd., 1978), a book written by the noted geologist William Fyfe, who died in 2013.

So, the rarity of diamonds has little to do with their elemental composition; rather, the natural transformation of carbon into diamonds that can be mined is an extremely arduous (and rarely successful) process.

"Diamonds can only be produced in the Earth's mantle and somehow be brought to the surface, or they can be formed during meteorite impact," but those diamonds are small and never gems, Fedortchouk said. (The mantle is the layer of Earth beneath the crust.)"Diamonds formed deep in the Earth's mantle can be brought up by deep magma or pushed up during the slow uplift of deep rocks during mountain growth processes. But during slow uplift, diamonds get graphitized [turned into graphite] and never make it up to the surface as gem stones."

The formula required for diamonds to form depends on depth, temperature and pressure: Carbon is buried at least 93 miles (150 kilometers) beneath the Earth's surface, heated to about 2,200 degrees Fahrenheit (1,204 degrees Celsius) under approximately 725,000 pounds of pressure per square inch (5 billion pascals), and then rapidly brought to the surface by a volcanic eruption to cool. This extraordinary process makes natural, minable diamonds rarer than gold, Fedortchouk said.

But, in its elemental form, gold is significantly rarer than diamonds, Faul told Live Science. After all, carbon is one of the most abundant elements on Earth — especially in comparison to heavier metals like gold — and diamond is simply composed of carbon under immense pressure.

The invention of synthetic diamonds complicates the question even further. Scientists can re-create the conditions necessary to transform graphite into diamonds in a lab — no volcanic eruption necessary — but the same can't be said for gold (sadly, alchemy is still a pseudoscience). Even though synthetic diamonds are made of the same substance as natural diamonds, according to diamond designer Ritani, synthetic diamonds usually sell for 30 percent less on the market because they aren't considered as valuable.

But does the mere existence of lab-created diamonds make these gems more common than we thought? Faul argues that it does: "Diamonds below a certain size are not worth mining in the first place," he said. "Who wants to buy a diamond that needs a magnifying glass to be seen? Gold is more abundant than large diamonds, but diamonds as a class of material are not particularly rare. I think part of their reputation has to do with amazing public relations!"

Originally published on Live Science.