Think you know rocks, minerals and gemstones?

Semi-precious rocks, minerals and gems
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How well-versed are you with our planet's fascinating geology? Test your knowledge and find out.

Question 1 of 16

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Sedimentary rock
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Which of the following is not one of the three types of rock?

The three types of rock are igneous, metamorphic and sedimentary. Minerals, on the other hand, are actually not rocks at all.

Rather, they are naturally occurring solid substances that are distinguished for their specific chemical composition and crystalline structure. A rock can contain one or more minerals, and in some cases, no minerals at all.

Question 2 of 16

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Travertine deposits in Pamukkale, Turkey
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Travertine terraces are composed of what kind of sedimentary rock?

Travertines are a type of limestone formed by mineral springs. The distinctive "terrace" appearance is created by the swift precipitation of calcium carbonate, which is one of the primary minerals that makes up limestone.

Question 3 of 16

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Iron pyrite, also known as fool's gold
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What is the name of this lustrous yellow specimen?

You're no fool if you picked pyrite! Despite its resemblance to gold, this brassy, pale yellow mineral is actually iron-based. Because of this, it is commonly known as "fool's gold."

Question 4 of 16

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Basaltic lava flow in Hawaii
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Which of the following is not an igneous rock?

Igneous rocks like pumice, basalt and obsidian are all formed through volcanic activity.

Gneiss, on the other hand, is formed by metamorphism and is known for its distinctive banding composed of pre-metamorphic sedimentary and igneous rocks.

Question 5 of 16

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A colorful collection of opals
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What do you call these colorful, milky gemstones?

Those brilliant, diffracting specks of light found within an opal are determined by the internal structure of each gem.

A staggering 90 percent of all the world's opals are found in Australia. It also happens to be the place of origin for the "Virgin Rainbow," which is touted as the world's finest opal.

Question 6 of 16

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Diamond and coal
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Which element is responsible for both coal and diamonds?

Although they are both composed of carbon, the idea that diamonds are formed from coal is actually a myth. Their origin stories are quite different in both time and scale.

Coal is a fossil fuel that is formed over millions of years from dead carbon-based lifeforms (primarily plants). On the other hand, diamonds, which are created from pure carbon sources, take billions of years to develop under intense metamorphic pressure.

Question 7 of 16

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Muscovite mica embedded with pink morganite
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What do you call the thin, flaky portion of this mineral?

Mica is a lightweight and relatively soft mineral characterized by its flaky silicate sheets. There are actually 37 different types of mica — the specimen pictured above is known as muscovite.

Question 8 of 16

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Talc
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What is the softest mineral?

Talc has a rating of "one" on Mohs' Scale of Hardness, and because of its physical qualities, it is often utilized in powder form as a deodorant or as a method for preventing diaper rash.

Question 9 of 16

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Feldspar
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What mineral makes up approximately 60 percent of the Earth's crust?

Constituting about 60 percent of all terrestrial rocks, feldspar is the most abundant type of mineral found within the Earth's crust. It is often found mixed with other minerals in rocks like granite.

Question 10 of 16

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Asbestos
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What lethal mineral is a serious cause for concern when found in older homes and buildings?

For the better part of the 20th century, asbestos' fibrous crystals were widely used as an affordable, fire-resistant insulation material in building and manufacturing. After discovering that the mineral was causing chronic respiratory diseases like lung cancer and mesothelioma, the mineral (pictured above as a solid lump) was gradually phased out.

Today, if homeowners or developers want to renovate or demolish a property built prior to the 1980s, they must take extra precautions to do so safely.

Question 11 of 16

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Holding a lump of coal
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What is an example of a rock that does not contain minerals?

By definition, all minerals are inorganic and possess a crystal structure. However, coal is a non-crystalline rock made up of organic carbon-based lifeforms. It is sometimes referred to as amorphous carbon, which means that it doesn't have a crystalline structure (unlike carbon minerals such as graphite or diamond).

Other examples of organic rocks and gems include amber (fossilied tree resin), coprolite (fossilized feces) and coquina (limestone composed of shells and coral).

Question 12 of 16

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Diamond drill
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No material is harder than a diamond.

Diamonds are still one of the hardest materials in the world, but in recent years, scientists have made several new advances. This includes the development of a man-made material known as aggregated carbon nanorods (ACNR), which is capable of scratching diamonds. Even so, we won't see diamonds going away anytime soon — they're still heavily depended upon for industrial cutting.

Question 13 of 16

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Tiger's eye stone
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What's the name for this semi-precious gemstone?

Tiger's eyes are quartz gemstones that are known for their silky reddish-brown chatoyancy — a reflective optical effect created by the stone's fibrous structure. The word "chatoyancy" comes from the French phrase "œil de chat," which means "cat's eye."

Question 14 of 16

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Beryl gem varieties: Aquamarine, morganite and emerald
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Aquamarine, emerald and morganite are all varieties of what kind of mineral?

Identified by its hexagonal crystal formations, pure beryl is colorless, but when it is tinted by impurities, it can take on colors like green, blue, yellow and red.

Question 15 of 16

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Bits of turquoise
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What is the name of this mineral?

Turquoise is an opaque, blue-green mineral that is composed of copper and aluminum. As one of the first gems ever mined by humans, it has a long history as a prized ornamental gem.

Question 16 of 16

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Antelope Canyon
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How was Arizona's Antelope Canyon formed?

The Navajo sandstone found within this iconic slot canyon was carved into its distinct, wavy shape over many years through erosion caused by flash floods.

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Semi-precious rocks, minerals and gems
Photo: Vladyslav Morozov /Shutterstock
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