托福阅读tpo61R-1原文+译文+题目+答案+背景知识

TPO61 阅读-1 Physical Properties of Minerals

原文 .................................................................................................................................................. 1

译文 .................................................................................................................................................. 2

题目 .................................................................................................................................................. 4

答案 .................................................................................................................................................. 7

背景知识........................................................................................................................................... 8

原文

Physical Properties of Minerals

①A mineral is a naturally occurring solid formed by inorganic processes. Since the

internal structure and chemical composition of a mineral are difficult to determine

without the aid of sophisticated tests and apparatus , the more easily recognized

physical properties are used in identification.

②Most people think of a crystal as a rare commodity, when in fact most inorganic

solid objects are composed of crystals. The reason for this misconception is that

most crystals do not exhibit their crystal form: the external form of a mineral that

reflects the orderly internal arrangement of its atoms. Whenever a mineral forms

without space restrictions, individual crystals with well-formed crystal faces will

develop. Some crystals, such as those of the mineral quartz, have a very distinctive

crystal form that can be helpful in identification. However, most of the time, crystal

growth is interrupted because of competition for space, resulting in an intergrown

mass of crystals, none of which exhibits crystal form.

③Although color is an obvious feature of a mineral, it is often an unreliable

diagnostic property. Slight impurities in the common mineral quartz, for example,

give it a variety of colors, including pink, purple (amethyst), white, and even black.

When a mineral, such as quartz, exhibits a variety of colors, it is said to possess

exotic coloration. Exotic coloration is usually caused by the inclusion of impurities,

such as foreign ions, in the crystalline structure. Other minerals — for example,

sulfur, which is yellow, and malachite, which is bright green — are said to have

inherent coloration because their color is a consequence of their chemical makeup

and does not vary significantly.

④Streak is the color of a mineral in its powdered form and is obtained by rubbing

a mineral across a plate of unglazed porcelain. Whereas the color of a mineral

often varies from sample to sample, the streak usually does not and is therefore

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the more reliable property.

⑤Luster is the appearance or quality of light reflected from the surface of a

mineral. Minerals that have the appearance of metals, regardless of color, are said

to have a metallic luster. Minerals with a nonmetallic luster are described by

various adjectives, including vitreous (glassy) pearly, silky, resinous, and earthy

(dull).

⑥One of the most useful diagnostic properties of a mineral is hardness, the

resistance of a mineral to abrasion or scratching. This property is determined by

rubbing a mineral of unknown hardness against one of known hardness, or vice

versa. A numerical value can be obtained by using Mohs' scale of hardness, which

consists of ten minerals arranged in order from talc, the softest, at number one, to

diamond, the hardest, at number ten. Any mineral of unknown hardness can be

compared with these or with other objects of known hardness. For example, a

fingernail has a hardness of 2.5, a copper penny 5, and a piece of glass 5.5. The

mineral gypsum, which has a hardness of two, can be easily scratched with your

fingernail. On the other hand, the mineral calcite which has a hardness of three,

will scratch your fingernail but will not scratch glass. Quartz, the hardest of the

common minerals, will scratch a glass plate.

⑦The tendency of a mineral to break along planes of weak bonding is called

cleavage. Minerals that possess cleavage are identified by the smooth, flat surfaces

produced when the mineral is broken. The simplest type of cleavage is exhibited by

the micas. Because the micas have excellent cleavage in one direction, they break

to form thin, flat sheets. Some minerals have several cleavage planes, which

produce smooth surfaces when broken, while others exhibit poor cleavage, and

still others exhibit no cleavage at all. When minerals break evenly in more than one

direction, cleavage is described by the number of planes exhibited and the angles

at which they meet. Cleavage should not be confused with crystal form. When a

mineral exhibits cleavage, it will break into pieces that have the same configuration

as the original sample does. By contrast, quartz crystals do not have cleavage, and

if broken, would shatter into shapes that do not resemble each other or the

original crystals. Minerals that do not exhibit cleavage are said to fracture when

broken. Some break into pieces with smooth curved surfaces resembling broken

glass. Others break into splinters or fibers, but most fracture irregularly.

译文

矿物的物理性质

①矿物质是由无机过程形成的天然固体。由于矿物的内部结构和化学组成如果

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没有精密的测试和仪器的帮助是很难确定的，所以在鉴定时使用比较容易识别的物理性质。

②大多数人认为晶体是一种稀有商品，而实际上大多数无机固体物体都是由晶体构成的。产生这种误解的原因是大多数晶体并不表现出它们的晶体形态:矿物的外部形态反映了其原子的有序内部排列。当一种矿物在没有空间限制的情况下形成时，就会形成具有良好晶面的单个晶体。有些晶体，如矿物石英，具有非常独特的晶体形式，有助于鉴定。然而，大多数时候，由于空间竞争，晶体生长被中断，导致相互生长的大量晶体，没有一个显示晶体形式。

③虽然颜是一种矿物的明显特征，但它往往是一种不可靠的诊断性质。例如，普通矿物石英中的轻微杂质会赋予它各种颜，包括粉、紫(紫水晶)、白，甚至黑。当一种矿物，如石英，表现出各种各样的颜时，人们就说它具有奇异的彩。奇异着通常是由于晶体结构中包含了杂质，如外来离子。其他矿物——例如黄的硫和亮绿的孔雀石——据说具有固有的颜，因为它们的颜是它们的化学组成的结果，变化不大。

④条纹是粉末状矿物的颜，是通过在一盘未上釉的瓷器上摩擦矿物获得的。虽然一种矿物的颜在不同的样品之间往往不同，但条纹通常不会，因此是更可靠的性质。

⑤光泽是指从矿物表面反射的光的外观或特性。具有金属外观的矿物，不论其颜如何，被称为具有金属光泽。有非金属光泽的矿物可以用各种形容词来描述，包括玻璃状珍珠般的、丝状的、树脂状的和土状的(暗淡的)。

⑥矿物最有用的诊断性的特性之一是硬度，即矿物对磨损或刮擦的抵抗力。这种性质是通过将一种硬度未知的矿物与一种硬度已知的矿物摩擦来确定的，反之亦然。用莫氏硬度计可以得到一个数值，莫氏硬度计由十种矿物组成，从最软的第1位滑石到最硬的第10位钻石。任何硬度未知的矿物都可以与这些矿物或其他硬度已知的物体相比较。例如，指甲的硬度是2.5，一枚铜币的硬度是5，一块玻璃的硬度是5.5。矿物石膏有硬度是2，很容易被指甲划伤。然而，矿物方解石硬度为3，会划伤指甲，但不会划伤玻璃。石英是最坚硬的普通矿物，它会划伤玻璃板。

⑦矿物沿着弱键合面断裂的趋势称为解理。具有解理的矿物是由矿物破碎时产生的光滑、平坦的表面识别出来的。最简单的解理类型是云母。因为云母在一个方向上有很好的解理，所以它们会断裂形成薄而平的薄片。有些矿物有好几个解理面，这些解理面在断裂时产生光滑的表面，而另一些矿物则表现出很差的解理，还有一些矿物则根本没有解理。当矿物向多个方向均匀破碎时，解理是由所显示的面数和它们相遇的角度来描述的。解理不应与晶体形式相混淆。当矿物显示出解理时，它会分裂成与原始样品具有相同结构的碎片。相比之下，石英晶体没有解理，如果断裂，就会碎裂成彼此或与原始晶体都不相似的形状。不表现解理的矿物在断裂时称为断裂。有些碎片表面光滑弯曲，类似破碎的玻璃。

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题目

word "apparatus" in the passage is closest in meaning to

A. equipment

B. procedures

C. experiments

D. laboratories

ing to paragraph 2, which of the following is a mistaken belief that people

have about crystals?

A. Crystals always have a well-formed shape.

B. Minerals are generally composed of crystals.

C. The atoms of a crystal have an orderly arrangement.

D. Crystals are always solid and inorganic.

ing to paragraph 3, how do different samples of the same mineral come to

exhibit a variety of colors?

A. The samples have different crystalline structures.

B. The samples contain different varieties of quartz.

C. The samples differ in the impurities they contain.

D. The samples were formed in different exotic conditions.

of the following can be inferred about streak from paragraph 4?

A. When a sample of a mineral is rubbed on unglazed porcelain, the color of the

streak is usually the same as the color of the sample.

B. In most cases, different samples of a mineral produce streaks that are all of the

same color even though the samples themselves are of different colors.

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C. When a streak is made. the impurities in the mineral are removed and the true

color of the mineral is revealed.

D. Streak color is reliable for identifying minerals because a given mineral sample

always yields the same color of streak each time it is rubbed.

can be inferred from paragraph 6 that the mineral quartz

A. has no fixed degree of hardness

B. might scratch the surface of a diamond

C. is harder than calcite

D. has atoms that are weakly bonded to each other

word "configuration" in the passage is closest in meaning to

A. effect

B. range

C. transformation

D. form

ing to paragraph 7, which of the following is true of the cleavage of micas?

A. Micas are the only minerals to break along planes of weak bonding.

B. Micas exhibit poor cleavage because they tend to break unevenly.

C. Micas break in one direction, forming thin sheets with smooth surfaces.

D. Micas break in several directions, forming a number of angles and planes.

does the author warn "Cleavage should not be confused with crystal form"?

A. Because most people have the mistaken belief that the surfaces of crystals are

planes of crystal cleavage

B. Because the author s characterization of cleavage in terms of smooth planes and

the angles between them could easily be mistaken for a description of crystal form

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C. To make the point that crystal form and cleavage are the same property only in

the simplest cases of cleavage, such as mica.

D. To introduce a discussion of minerals the have cleavage but not crystal form

at the four squares[■]that indicate where the following sentence could be

added to the passage. Where would the sentence best fit? Click on a square[■]to

add the sentence to the passage.

Each mineral has an orderly arrangement of atoms (crystalline structure) and a

definite chemical composition that give it a unique set of physical properties..

①A mineral is a naturally occurring solid formed by inorganic processes. [■]Since

the internal structure and chemical composition of a mineral are difficult to

determine without the aid of sophisticated tests and apparatus, the more easily

recognized physical properties are used in identification. [■]

②Most people think of a crystal as a rare commodity, when in fact most inorganic

solid objects are composed of crystals. [■]The reason for this misconception is

that most crystals do not exhibit their crystal form: the external form of a mineral

that reflects the orderly internal arrangement of its atoms. [■]Whenever a

mineral forms without space restrictions, individual crystals with well-formed

crystal faces will develop. Some crystals, such as those of the mineral quartz, have

a very distinctive crystal form that can be helpful in identification. However, most

of the time, crystal growth is interrupted because of competition for space,

resulting in an intergrown mass of crystals, none of which exhibits crystal form.

ions: An introductory sentence for a brief summary of the passage is

provided te the summary by selecting the THREE answer choices

that express the most important ideas in the passage. Some sentences do not

belong in the summary because they express ideas that are not presented in the

passage or are minor ideas in the passage. Drag your answer choices to the spaces

where they belong. To remove an answer choice, click on review the passage,

click VIEW TEXT

Minerals have a number of physical properties, some of which are useful for

mineral identification.

minerals show a characteristic crystal form that results from the way their

atoms are arranged in the crystal structure.

is a good guide to the identity of glassy and metallic minerals, but not

those that have dull or earthy appearance.

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minerals characteristically split along one or more smooth planes of

cleavage while others typically fracture unevenly.

many minerals, the streak formed by a rubbing a mineral sample on unglazed

porcelain is a more reliable guide for identification that the color of the sample.

relative hardness of a mineral as determined by Mohs scale is very useful for

identifying a mineral sample.

has a characteristic crystal form, but no cleavage and its color varies

widely from sample to sample, all of which make it a typical mineral.

答案

1-5.A A C B C

6-9.D C B A

10. CDE

小结题解析

答案 CDE。

A 错误，第二段第二句话提到 most crystals do not exhibit their crystal form，选项描述与原文相反。

B 错误，第五段提到 luster 是一种外观呈现，不同物质的外观不同，但并未提到 Luster is a good guide，更未提到有些物质不具备 luster。

C 正确，第七段中提到的信息：Some minerals have several cleavage planes,

which produce smooth surfaces when broken；最后一句 Others break into

splinters or fibers, but most fracture irregularly，也可以体现有些碎裂时是不均匀的。

D 正确，第四段中讲到 streak 时提到 the streak usually does not varies and is

therefore the more reliable property，所以选项描述符合。

E 正确，第六段提到首句提到 one of the most useful diagnostic properties of a

mineral is hardness，而且第三句中也提及了量化硬度可以参考 Mohs' scale of

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hardness。所以该选项描述符合文本内容。

F 错误，第二段提到 mineral quartz have a very distinctive crystal form，即独特的晶体结构；第三段提到 When a mineral, such as quartz, exhibits a variety of

colors, it is said to possess exotic coloration，即颜种类多；第七段提到了 quartz

crystals do not have cleavage，没有 cleavage。但是这些信息都是关于 quartz 的性质，文本主旨介绍的一般矿物质的各种物理性质，相较于其他选项为细节类信息，关于 quartz 性质的内容相对次要细节，故而不选。

背景知识

矿物的物理性质有很多方面，主要介绍不需借助仪器即可观察的性质

矿物的物理性质和矿物形态一样，也是矿物的化学成分、内部结构和形成条件的综合反映。它是肉眼鉴定矿物的主要依据，因不同矿物可具相同形态，且完好形态的晶体少见，而物理性质既固定又易识别。

矿物的物理性质有很多方面，下面主要介绍一些不需借助仪器即可观察或测定的性质。

（一）颜和条痕

颜是矿物最直观的性质之一，通常分为以下三类：

1.自 在成因上与矿物本身的固有化学成分直接有关的颜。例如黄铜矿的深黄铜，孔雀石的翠绿，蔷薇辉石的粉红等等。矿物的自相当固定而具有特征性。上述几种矿物的名称就与它们的颜有关。

2.他 由非矿物本身固有的组分所引起的颜。例如纯净的刚玉为白，当含有微量的类质同象替代元素Cr3＋时便呈鲜红（红宝石），含Ti 4＋时呈蓝（蓝宝石）。他也可因含有染杂质的细微机械混入物而产生，且颜随杂质组分的不同而异。

矿物粉末的颜称为条痕，因为通常是将矿物在素瓷板上摩擦以观察其留下的粉末痕迹的颜。对一种矿物来说，其条痕的呈通常都是固定的，且可以不同于矿物块体的颜。例如金的条痕为金黄，而黄铜矿的条痕则为绿黑。

（二）光泽

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光泽系指矿物表面对可见光的反射能力。通常将光泽自强而弱分为以下四级：

1.金属光泽 反射很强，如同镀了克罗米的平滑金属表面那样的反光。

2.半金属光泽 反射强，如同一般金属表面那样的反光。

3.金刚光泽 反射较强，如金刚石般的灿烂反光。

4.玻璃光泽 反射强，如同玻璃板表面那样的反光。

以上都是指矿物在平坦面上的反光。如矿物表面不平坦光滑或成集合体时，就会出现一些特殊的光泽，有油脂光泽，树脂光泽，蜡状光泽，土状光泽，丝绢光泽和珍珠光泽。其中土状光泽也就是光泽暗淡，或者说无光泽，而丝绢光泽只出现在纤维集合体上。

（三）硬度

物体抵抗外力机械作用的强度称为硬度。在矿物学中作一般测定时都采用所谓的摩斯（Mohs）硬度计。它是以选定10种矿物为标准，将它们的硬度分别定为1到10，即：

1滑石 2石膏 3方解石 4萤石 5磷灰石

6正长石 7石英 8黄玉 9刚玉 10金刚石

等级越高，硬度便越大，金刚石是迄今已知物体中硬度最大的。但摩斯只是相对硬度，逐级间的差值并不相等，例如按所谓的维克尔硬度计算，石英是滑石的560倍，而金刚石则是滑石的约5000倍。

通常还可借助于其他常见物体的帮助来测定矿物的硬度。例如已知指甲的硬度为2＋，铜钥匙约为3，小钢刀为5＋，窗玻璃为5.5，钢锉为6.5，都可作为辅助标准。

（四）解理和断口

晶体在受到应力作用而超过弹性极限时，能沿着一定方向的面网发生破裂的固有特性，称为解理；沿解理裂成的平面称为解界面。

矿物晶体或其集合体，若无规则地沿着除解理面以外的方向破裂时，其断裂面称为断口。

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（五）比重

比重是人们很熟悉的一项物性。矿物的比重可以从小于1（如琥珀）一直到约23（铂族自然元素矿物）。通常可凭经验用手掂量，将矿物的比重很粗略地分为轻、中和重三等。绝大多数矿物的比重属中等，即介于2.5~4之间。但有些矿物，如方铅矿（7.4~7.6）、黑钨矿（7.1~7.5）、锡石（6.8~7.0）以及金属自然元素矿物，具有特大的比重，成为它们一项突出的特性。

此外，经常也将矿物区分为重矿物和轻矿物两大类。凡在三溴甲烷液体中下沉的，即比重大于2.9的，均归属于重矿物。

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