5. Перескажите вкратце содержание текста The Properties of Minerals, используя следующие ключевые слова:

a characteristic attribute

the most important properties

regular pattern

geometrical relationship

angles between the faces

the crystal face

the full symmetry

the twinning plane

TEXT 2.3.

VOCABULARY WORK:

• Запомните следующие слова:

Научный вокабуляр:

submetallic [‚sAbme'txlIk] - субметаллический

opaqueness [qu'peIknqs] - непрозрачность, светонепроницаемость

pyrite ['paIraIt] - пирит, серный (железный) колчедан

cleavage ['klJvIG] - кливаж, слоистость, расщепление

graphite ['grxfaIt] - графит

transparency [trxns'pxrqnsI] - прозрачность, светопроницаемость

translucency [trxns'lHsnsI] - светопрозрачность, полупрозрачность

calcite ['kxlsaIt] - кальцит, известковый шпат

Общеязыковой вокабуляр:

examination [Ig‚zxmI'neISn] - исследование, изучение

display [dI'spleI] - обнаруживать, проявлять

irrespective [‚IrI'spektIv] - безотносительный, независимый

weak [wJk] - слабый, непрочный

brassy ['brRsI] - латунный; медный

rainbow ['reIn‚bqu] - радуга

dull [dAl] - тусклый, неяркий

weakness ['wIknqs] - непрочность, слабость

hit [hIt] - ударять (по чему-л.)

hammer ['hxmq] - молот, кувалда; молоток

splitting ['splItIN] - расщепление, раскалывание

octahedral [‚Oktq'hJdrql] - восьмигранный, октаэдральный

prismatic [prIz‚mxtIk] - призматический

basal [‚beIsql] - базальный, основной

cubic ['kjHbIk] - кубический

rhombohedral [‚rOmbqu'hJdrql] - ромбоэдрический

provide [prq'vaId] - обеспечивать

be alike [q'laIk] - быть подобным

ease [Jz] - лёгкость, простота

pry [praI] - вскрывать

knife [naIf] - нож

imperfect [Im'pE:fIkt] - несовершенный, дефектный

poor [puq] - плохой, недостаточный

indistinct [‚IndI'stINkt] - неясный

• Прочтите следующий текст и переведите его:

Colour. Luster. Transparency and Cleavage

Complete identification of many minerals can be made thorough their physical properties examination. As we have already learnt, the main mineral properties are electrical and magnetic properties, crystal form, state of aggregation, fracture, cleavage, hardness, specific

gravity, surface energy, taste and smell, and the properties dependent on light, such as lustre, colour, refraction, double refraction, extinction and pleochroism.

Colour

The first feature of a mineral which catches the eye is, in all probability, its colour. Some minerals at all times have the same colour irrespective of where the mineral is found.

For instance, graphite is constantly black, pyrite is always brassy. The other minerals may display any colour of the rainbow. The mineral may have its true colour or its colour may be the result of an impurity mixed with it.

Luster

Luster refers to the way in which light is reflected from the mineral surface. This property is of considerable assistance when identifying most minerals.

Luster can be of two main classes: non-metallic and metallic, for example, the luster of opaque metals such as iron, steel, lead.

In case it is difficult to determine for sure whether the mineral luster is metallic or non-metallic, such a luster is termed submetallic.

Transparency

This term presupposes three mineral properties: transparency, translucency and opaqueness.

Transparency means permitting the uninterrupted passage of light. The objects are clearly visible through the transparent mineral.

Translucency means allowing light to pass through partially or diffusely. The light passes through the translucent mineral but it is impossible to recognize objects.

Opaqueness means, first of all, not transmitting light, not transparent or translucent and, secondly, not reflecting light, lacking lustre or shine, dull. No light passes through the opaque mineral.

Structure

The term “structure” means the way in which a mineral, rock, rock mass or stratum is made up of its component parts. This term describes crystalline mineral masses.

This property is very helpful when identifying minerals. Some minerals are weak in certain respects. They can break when hit with a hammer to show flat shiny surfaces. The weakness that causes these breaks is called cleavage, that is the certain rocks natural splitting. The minerals may possess cubic, octahedral, prismatic, basal, rhombohedral cleavage and others.

One more factor that is sometimes important is the cleavage directions angle. Knowing whether the directions are at the right angles or not provides valuable information since two minerals may be alike but for their cleavage angles.

All cleavage is not easy to bring about and there are terms to describe ease of cleavage. Perfect cleavage is usually caused by a light blow inflected on the mineral or if it is pried gently with a knife. For example, mica, galena and calcite have perfect cleavage. Distinct cleavage calls for a heavier blow. The cleavage also can be easy, imperfect, poor and indistinct.

Комментарии к тексту:

catch [kxC] the eye [aI] - привлечь внимание

determine [dI'tE:mIn] - определить

for sure [Suq] - бесспорно

uninterrupted [‚AnIntq'rAptId] passage ['pxsIG] of light [laIt] - непрерывное пропускание света

partially ['pRSqlI] or diffusely [dI'fjHzlI] - частичный или рассеянный

in certain ['sE:tn] respects [rI'spekts] - в некоторых отношениях

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