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8 Structure Secrets of Gemstones

People value gemstones for all sorts of reasons.
宝石通常都很稀有 十分稳定耐久 最重要的是他们都闪亮耀眼
They’re usually rare, pretty durable, and most of all, they’re shiny and sparkly.
它们的颜色多种多样 形态各异 具有各种光学效应
They can have multiple colors, streaks of light, weird inside-out shapes,
and all kinds of other qualities.
The things we consider gemstones are often made up of minerals arranged into different
types of crystals, although a few are made up of molecules that are arranged totally randomly.
但是无论由何种方式组成 它们的性质都源于它们的化学结构
But either way, their properties come from their specific chemical structure.
在原子层面 这是简单的几何形状
At the atomic level, it’s simple geometry.
But it leads to some of the most beautiful natural materials on Earth.
当你观察一块宝石 你可能注意到的第一件事就是它的颜色
When you look at a gemstone, probably the first thing you notice is its color.
一些宝石 如碧玺和萤石
Some gems, like tourmaline and fluorite, can
come in practically any color you can think of.
通常 这些颜色是过渡金属元素和矿物晶体结构
And often, those colors come from transition metals that are incorporated into the mineral’s
共同作用的结构——金属元素如铜 铁和锌
crystal structure — metals like copper, iron, and zinc.
The transition metals are the metals in the middle part of the periodic table.
这些元素倾向于表现明亮的颜色 因为它们电子的分布
Those elements tend to take on bright colors because the way their electrons are arranged
lets them absorb visible light with certain wavelengths.
当这些波长的光线被吸收 我们可以看到与之互补的颜色
With those wavelengths gone, we see a complementary color.
有时 某种特殊金属元素是该矿物结构的固有组成部分
Sometimes, a specific metal is an inherent part of a mineral’s structure,
so the mineral always takes on that color.
比方说 孔雀石 在它的化学结构中
Malachite, for example, has copper in its
chemical structure, which turns it green.
有时 这些金属元素并非矿物的固有组成
Other times, the metals aren’t an inherent part of the mineral.
相反 它们是矿物晶体结构中的杂质
Instead, they’re sort of hitchhiking in its crystal structure, occasionally taking
the place of whatever element would normally be there.
例如 红宝石和蓝宝石
Ruby and sapphire, for example, are actually
实际上是同一种矿物 叫做刚玉 化学式为Al2O3
the same mineral, called corundum, with a chemical formula of two aluminums and three oxygens.
当一些铁原子和钛原子取代了一些铝原子时 矿物呈亮蓝色
When some iron and titanium atoms replace a few of the aluminums, the mineral is brilliant
blue. That’s what we call that a sapphire.
But when the hitchhiking atoms are chromium instead,
矿物颜色变为红色 这样你就有了一块红宝石
the mineral turns red and you have a ruby.
但是就颜色而言这里还有不少内容 原因是宝石通常不止一种颜色
But there’s more to this color thing, because gems aren’t always just one color.
Some look like they change color when you
view them from different angles, an effect that’s known as pleochroism.
看 晶体是由图案重复排列的原子组成的
See, crystals are made up of atoms arranged in repeating patterns.
这些图案组成的小块称作晶胞 晶胞有不同的形状
The patterns form blocks called unit cells, which can be different shapes,
like cubes or pyramids.
Geologists classify crystals by assigning three axes to the unit cell.
晶体所具有的不同形状和性质 取决于这些晶轴是否相互垂直
Depending on whether those axes are at right angles to each other or not, and whether they’re
the same length or not, crystals will have different shapes and properties.
It’s kind of like the difference between building a tower with cube-shaped blocks and
building one with pyramid-shaped blocks.
They’re gonna be different.
如果晶轴之间长度相等且相互垂直 就像在一个
If the axes are all the same length and at right angles to each other, like in a cubic
立方体的晶胞中 那么当光穿过晶体 没有什么有趣的效应会发生
unit cell, nothing very interesting will happen to the light passing through the crystal.
但当这些晶轴彼此不同 那么当光线
But when the axes are different, the light can get split into multiple paths
as it travels through the crystal.
Different paths might absorb more of different colors of light.
所以打个比方来说 光线从一条路径透入 晶体可能看上去偏绿色
So for example, light traveling along one path might seem more green, and along another
但从另一条透过 晶体可能看上去偏棕色
it might look more brown.
当你旋转晶体 你改变的是光透过的路径
And when you rotate the crystal, you change the paths the light takes.
所以当你动一动头 或者在手中转动晶体
So pleochroic crystals seem to change color
as you move your head, or rotate them in your hand.
你可以得到两种或者三种不同的颜色 取决于它们实际的形状
Depending on their exact geometry, you can get either two or three different colors.
并不是所有非等轴晶系的宝石都具有多色性 并且即便它们具有这一性质
Not all non-cubic gems are pleochroic, and even when they are, the color change isn’t
always noticeable to our eyes.
But it’s a pretty common property.
比如 蓝宝石 常常具有多色性
Sapphire, for instance, is often pleochroic.
So is topaz.
It’s just light interacting with atomic geometry.
But it looks awesome.
然后 有些宝石在磁场作用下会被吸引或排斥
Then there are gems that are attracted or repelled by a magnetic field.
You can’t just walk up to your refrigerator and stick a garnet to it or anything, but
strong magnets will attract certain kinds of gems.
事实上 过渡金属元素赋予了宝石颜色 同样使它们被磁体吸引
In fact, the same transition metals that give gems their color can make them drawn to magnets.
通常 造成这种情况的金属元素是铁
Often, the metal responsible is iron,
but rare earth elements like neodymium can do it too.
Those trace elements make the mineral magnetic because they have odd numbers of electrons.
电子具有一种性质 叫做自旋 而且两个反向自旋
Electrons have a property called spin, and two electrons
with opposite spins pair up and cancel out.
但是 当一个电子没能配对 它的自旋则没有被抵消
But when an electron isn’t paired, its spin goes un-canceled, and it’s free to be attracted
by a passing magnetic field.
That’s called paramagnetism.
另一方面 所有电子都配对的材料对磁场有轻微的排斥
On the other hand, a material with all its electrons paired up is slightly repelled by
因为当电子在原子内部运动时 它们自身产生了
a magnetic field, because when the electrons move around in an atom, they make magnetic
一个磁场 这个磁场排斥了其他磁体
fields of their own, which repel other magnets.
That’s diamagnetism.
比如铋就具有逆磁性 所以它总是被磁体排斥
Bismuth, for instance, is diamagnetic, so it’s always repelled by a magnet.
When unpaired electron spins line up parallel
你将见到铁磁性 或者一个实际上是磁体的矿物
to each other, you get ferromagnetism, or a mineral that’s an actual magnet.
具有铁磁性的矿物很少 但赤铁矿是一个例子
Very few minerals are ferromagnetic, but hematite is one example.
有时 一个通常被磁体排斥的宝石如果含有少量铁元素
Sometimes, a gem that’s normally repelled by magnets will have bits of iron inside it,
which will make it attracted to magnets instead.
So magnetism isn’t a perfect tool for figuring out what a gem is made of.
But it’s often a helpful clue.
You’ll often see gems cut into facets, but
但其他时候 它们将会被抛光成圆润的弧形 这被称为弧面形琢型
other times, they’ll be polished into a round shape called a cabochon.
有时 弧面型宝石会看到一条明亮的光带
And sometimes, a round-polished gem will look like it has a bright streak of light across
穿过它的表面 像一只猫的眼睛中竖直的瞳孔
its surface, like the vertical pupil in a cat’s eye.
这被称为猫眼效应 而且这种效应的产生源于
It’s called chatoyance, and it happens because
宝石内部的线状片晶 如金红石
of little thread-like pieces of a mineral, like rutile, inside the gem —
what scientists call silk.
正如这些晶体的组成 杂质原子沿着晶体结构中的晶轴排成一列
As these crystals form, the impurities are forced to line up along the axes of the crystal’s
structure, so the pieces of mineral end up parallel to each other.
这些平行的片晶反射光线 使得宝石表面
Those parallel pieces reflect light
in a way that creates a bright line perpendicular to the threads.
这并非宝石特有的现象 一卷丝线也会产生类似的效应
And it’s not just gems that do this — a spool of silk thread will do the same thing,
where there’s a streak of light perpendicular to the wound-up thread.
但与一卷丝线不同 宝石内部可能有不同方向的包裹体
But unlike a spool of thread, gems can have inclusions going in different directions,
based on the crystal structure of the mineral.
That creates a streak of light perpendicular
看上去就像一个含有四条 六条或更多条的星星
to each axis, which looks like a star with four, or six, or even more points.
The star effect is called an asterism.
当一块宝石拥有这些线状包裹体 切割成刻面型可能使它看上去有些模糊
When a gem has these threads, cutting it into facets might make it look kind of muddy.
但是如果将它抛光成弧面型 你将看到绚丽的光带
But when it’s polished into a round shape, you get gorgeous streaks of light.
Polymorphic minerals don’t always have the same structure.
即便它们有着相同的化学成分 它们形成时
Even if they have the same chemical composition, the temperature and pressure when they form
can lead to different shapes.
Carbon is probably the most famous example of this.
碳可以形成柔软光滑的石墨或基本上坚不可摧的钻石 这取决于其原子排布
Depending on how its atoms are arranged, carbon can form soft, slippery graphite or basically-indestructible diamond.
Silica, the mineral that makes up sand and quartz, also has lots of different polymorphs.
Its molecular formula is always the same: one silicon atom and two oxygen atoms.
Its molecules form tetrahedral shapes — that’s a triangular pyramid,
or a d4 if you’re into tabletop RPGs.
Tetrahedrons can stack into different shapes as changes
in temperature and pressure juggle them around.
在人类适宜的温压条件下 二氧化硅形成α-石英
At the temperatures and pressures humans find comfortable, silica makes the alpha,
or so-called “low”, form of quartz.
But as temperature and pressure increase,
它可以形成出现在熔岩流中的方石英 或者
it can become things like cristobalite, which is found in lava flows, or stishovite, which
is in meteorite craters.
Even a single polymorph of silica can take on a huge variety of forms.
α-石英可以看起来像权杖 圆鹅卵石 或是成簇的针状物
Alpha quartz can look like scepters, rounded pebbles, or clusters of needles.
It all depends on the growth conditions: like how fast the crystals form, how much space
成晶空间的大小 以及成晶材料的多寡
is available, and how much material there is to make crystals.
晶胞以同样的方法堆积起来 但有时 某种杂质物质将导致
The unit cells stack together in the same way, but sometimes an impurity will cause
它们在某个角度分开 或者使它们
them to take off at an angle or make them more likely to stick to
one part of the crystal than another.
石英的种类太多以至于大量宝石——如紫水晶 玉髓 玛瑙和黄水晶
Quartz is so varied that tons of gems — like amethyst,
chalcedony, agate, and citrine — are all made of silica.
Organic matter can be slowly replaced by minerals to become a fossil.
通常 参与其中的矿物有些单调 但有时
Often, the mineral involved is kinda drab, but sometimes the conditions are just right
时机正好 从而会产生一些珍品
to produce something spectacular.
在极少数情况下 木变石 贝壳 牙齿
And in rare cases, petrified wood, shells, teeth,
甚至是灭绝生物的骨骼 都形成了欧泊
and even bones of extinct organisms are made of opal.
同世界上大多数的欧泊一样 硅化化石也大多在澳大利亚被发现
Opalized fossils are most often found in Australia, along with most of the world’s opal in general.
One of the most famous specimens is a pliosaur
nicknamed Eric, an almost-complete marine reptile preserved in opal.
同石英一样 欧泊由二氧化硅组成
Like quartz, opal is made of silica.
但同石英不同的是 它并不具备晶体结构
But unlike quartz, it doesn’t have a crystal structure.
反而 它是由小型的球状硅粒聚在一起形成的
Instead, it’s made of little spheres of silica all bunched together.
这些小球状体分散了光线 赋予了欧泊最具特色的五彩光泽
These tiny spheres scatter light, giving opal its characteristic rainbow sheen.
Geologists have a few different models for how opal might form, but it could come from
silica weathering out of rocks in an acidic environment.
Australia used to be partially covered by an inland sea.
而当这片海洋干涸时 它遗留下酸性的 含硅量高的凝胶
And as that sea dried up, it left acidic, silica-rich gel behind.
少量二氧化硅沉淀在凝胶中 之后成长为构成欧泊的球状体
Bits of silica settled into the gel and then grew into the spheres that make up opal.
有时 这种凝胶留存在骨骼中或是少量已经开始变成化石的木材里
Sometimes, that gel was stuck in bones or bits of wood that had already started to fossilize,
so the silica trapped in there formed opals in the shape of those organic structures.
这些化石产物具有美学和科学的双重价值 1993年
The resulting fossils have both aesthetic and scientific value, and in 1993, Eric the
pliosaur was almost made into jewelry by a broke owner looking to sell
and potentially break up the pieces.
但是一场众筹运动拯救了“埃里克” 并将它珍藏在澳大利亚博物馆
But a crowdfunding campaign rescued Eric and got him a place in the Australian Museum.
Hopper crystals are probably some of the strangest-looking crystals.
它们发育成一种奇特的阶梯状 有点像中空的金字塔的形状 这种形状被称为锥形
They’re shaped into a weird stair-stepped, hollow kind of pyramid known as a hopper.
The shape comes from a quirk of chemistry as the crystal is forming.
When the growth rate and saturation of the crystal-forming solution is just right, new
molecules will tend to be more attracted to the edges of the growing crystal
than the inner flat surfaces.
这使得其边缘的生长过快失去控制 而扁平的表面几乎保持不变
That makes the edges grow out of control while the flat faces mostly stay the same, so the
所以晶体的生长是以一种不平衡的方式进行 这造就了其内外不一的美妙形态
crystals grow in a lopsided way that leads to that fascinating inside-out shape.
铋锥晶必须要在实验室中生成 但锥形晶也可以在
Bismuth hopper crystals have to be grown in the lab, but hopper crystals have also been
自然界和天然矿物中发现 如玫瑰石英
found in nature, in minerals like rose quartz.
铋相当容易获得 而且其熔点低 所以实际上
Bismuth is pretty easy to get your hands on and has a low melting point, so you can actually
如果你足够大胆 你可以尝试去制作属于自己的锥形晶
try to make your own hopper crystals, if you’re feeling adventurous.
有些材料在文化意义上被视为矿物 但从严格的宝石学角度上
Some materials that are culturally prized as gems aren’t minerals or gems in the strictest
它们并非矿物或宝石 例如:琥珀 煤精 珊瑚和珍珠
geological sense: things like amber, jet, coral, and pearl.
这些材料多半具有非晶形的化学结构 而非由晶体构成
Instead of being made up of crystals, all these materials have more amorphous chemical
而且它们源于生物 这就是它们被称作非晶形的有机物的原因
structures, and they come from living things — that’s why they’re called amorphous organics.
But the way they form makes them look a lot like the classic crystal gems.
琥珀是经由树脂的石化作用而形成的 并且能实实在在地保留留存在其内部的有机物
Amber is fossilized tree resin, and can actually preserve organisms that get stuck in it.
当树脂被埋藏在稳定 潮湿 低氧的环境下时 它逐渐变为琥珀
When the resin gets buried in calm, wet, low-oxygen environments, it slowly turns to amber.
在某些方面 煤精和煤实际上是同种物质
Jet is practically the same thing as coal in some ways.
But while coal forms in big seams from huge amounts of plant material, jet is formed from
small bits of wood that get buried in sediment and compacted.
Jet can be cut and polished to a gem-like shine.
But it doesn’t have a rigid crystal structure — at a microscopic level, it can actually
preserve the cellular shapes of the plant it used to be.
Coral is made up of small colonial animals, with calcium carbonate skeletons.
珊瑚虫的骨骼通常为白色 但是常被视为宝石的珍贵珊瑚
The skeletons are usually white, but the precious coral that’s often considered a gem is a
species that includes reddish-orange carotenoid pigments.
Pearls contain a mixture of protein and calcium carbonate secreted by certain types of molluscs.
不同物种的软体动物会产出不同颜色的珍珠 而水中的杂质
Different species will produce different colors of pearls, and impurities
in the water can also affect the color.
正如在此名单上的所有宝石 非晶形的有机物有此外观
Like all of the gems on this list, amorphous organics look the way they do because of the
way their atoms are arranged.
The regimented structure of a crystal and the laid-back chaos of an amorphous solid
共同影响了它们同光线 磁场和其他材料的相互作用
both affect the way they interact with light, magnets, and other materials.
It’s the sparkliest kind of geometry.
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