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Diamonds, an occasional component of rare igneous rocks called lamproi

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Diamonds, an occasional component of rare igneous rocks called lamproi  [#permalink]

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New post Updated on: 14 Oct 2019, 04:13
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Diamonds, an occasional component of rare igneous rocks called lamproites and kimberlites, have never been dated satisfactorily. However, some diamonds contain minute inclusions of silicate minerals, commonly olivine, pyroxene, and garnet. These minerals can be dated by radioactive decay techniques because of the very small quantities of radioactive trace elements they, in turn, contain. Usually, it is possible to conclude that the inclusions are older than their diamond hosts, but with little indication of the time interval involved. Sometimes, however, the crystal form of the silicate inclusions is observed to resemble more closely the internal structure of diamond than that of other silicate minerals. It is not known how rare this resemblance is, or whether it is most often seen in inclusions of silicates such as garnet, whose crystallography is generally somewhat similar to that of diamond; but when present, the resemblance is regarded as compelling evidence that the diamonds and inclusions are truly cogenetic.
The author implies that silicate inclusions were most often formed

(A) with small diamonds inside of them
(B) with trace elements derived from their host minerals
(C) by the radioactive decay of rare igneous rocks
(D) at an earlier period than were their host minerals
(E) from the crystallization of rare igneous material


Spoiler: :: OA
D


According to the passage, the age of silicate minerals included in diamonds can be determined due to a feature of the

(A) trace elements in the diamond hosts
(B) trace elements in the rock surrounding the diamonds
(C) trace elements in the silicate minerals
(D) silicate minerals' crystal structure
(E) host diamonds' crystal structure


Spoiler: :: OA
C


The author states that which of the following generally has a crystal structure similar to that of diamond?

(A) Lamproite
(B) Kimberlite
(C) Olivine
(D) Pyroxene
(E) Garnet


Spoiler: :: OA
E


The main purpose of the passage is to

(A) explain why it has not been possible to determine the age of diamonds
(B) explain how it might be possible to date some diamonds
(C) compare two alternative approaches to determining the age of diamonds
(D) compare a method of dating diamonds with a method used to date certain silicate minerals
(E) compare the age of diamonds with that of certain silicate minerals contained within them


Spoiler: :: OA
B


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Originally posted by carcass on 12 Jan 2019, 05:33.
Last edited by SajjadAhmad on 14 Oct 2019, 04:13, edited 1 time in total.
Updated - Complete topic (975).
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Re: Diamonds, an occasional component of rare igneous rocks called lamproi  [#permalink]

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New post 14 Jan 2019, 21:10

+1 kudos to the posts containing answer explanations of all questions


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Re: Diamonds, an occasional component of rare igneous rocks called lamproi  [#permalink]

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New post 15 Jan 2019, 02:19
1
2 mins 58 secs... all correct. Great short passage carcass, as usual, your passages are a treat to solve :-) Kind of felt similar to the movie Inception :-)

Diamonds have never been dated satisfactorily, however, some diamonds contain minute inclusions of silicate minerals - which can be dated fairly accurate due to radioactive decay of minute radioactive materials within those minerals. The passage goes on to mention that most silicate mineral impurities are older than the diamonds but a particular type "Garnet" has a structure very similar to the diamond and cab thought of as cogenetic.


The author implies that silicate inclusions were most often formed
(A) with small diamonds inside of them Opposite is true - some diamonds have silicate material inside them
(B) with trace elements derived from their host minerals nonsensical, discard.
(C) by the radioactive decay of rare igneous rocks Again, the two things are not related
(D) at an earlier period than were their host minerals Perfect - this is verbatim from the passage
(E) from the crystallization of rare igneous material not mentioned anywhere in the passage

Easy detail question, literally doable in under 10 secs :-)
According to the passage, the age of silicate minerals included in diamonds can be determined due to a feature of the
(A) trace elements in the diamond hosts Not there yet
(B) trace elements in the rock surrounding the diamonds Out of scope, rock surrounding diamonds what?
(C) trace elements in the silicate minerals Bingo - the characteristic being talked about is radioactivity and trace radioactive elements are present inside the silicate crystals which are inside the diamonds which are inside the igneous rocks! Kind of feels like the movie inception :-D
(D) silicate minerals' crystal structure not related to crystal structure
(E) host diamonds' crystal structure discard for same as above

It doesn't get easier than this ;-)
The author states that which of the following generally has a crystal structure similar to that of diamond?
(A) Lamproite
(B) Kimberlite
(C) Olivine
(D) Pyroxene
(E) Garnet Tick

Finally a challenging question - we need to realize that the main point of the passage is revealed right at the start - "now some diamonds can be dated accurately" is the main point
The main purpose of the passage is to
(A) explain why it has not been possible to determine the age of diamonds TRAP - a play of words - the author does not want to dwell too much on the past but has made a passing reference
(B) explain how it might be possible to date some diamonds Perfect - this is the reason why the author has written the passage
(C) compare two alternative approaches to determining the age of diamonds No two methods given
(D) compare a method of dating diamonds with a method used to date certain silicate minerals Again - flawed for same reason as above
(E) compare the age of diamonds with that of certain silicate minerals contained within them We are not comparing anything!

Hope my answers are helpful.
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Re: Diamonds, an occasional component of rare igneous rocks called lamproi  [#permalink]

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New post 15 Jan 2019, 02:21
riyarush2007 wrote:
I completed this Passage in 4:49 seconds with 75% accuracy (3/4) questions correct. Is the timing good?


The passage had only one challenging question - Q4. So even though the accuracy of 75% is great, I feel this passage deserves a 100% :-)

Again, 4 questions in 4mins 49 secs is good timing, keep it up! :-)
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Re: Diamonds, an occasional component of rare igneous rocks called lamproi  [#permalink]

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New post 16 Jan 2019, 11:08
1
PeepalTree, I guess I liked the topic. I have found that how you receive the topic has a lot to do with what accuracy you might get and how quickly you can go through the passage and the questions. Something consistently repeated by all the test prep companies - "attack the topic", "read actively", "imagine that you love the topic being discussed" etc. Easier said than done, but sometimes a passage comes out of the blue that just strikes as readable.

This is what I could think of.

Also, a few minutes saved can be used elsewhere. That is all the utility there is to solving fast - nothing more nothing less. Accuracy is paramount. :-)
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Re: Diamonds, an occasional component of rare igneous rocks called lamproi   [#permalink] 16 Jan 2019, 11:08
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