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Rocks & the rock cycle: Earth Science Regents Practice

Practice Rocks & the rock cycle for the Earth Science Regents with real-style questions and full worked solutions. Miss one? Read the solution — the exam reuses the same ideas every year.

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Question 33 · 2 pts

A mineral has a metallic luster, a hardness of about $2.5$, breaks along cubic cleavage planes, and is mined as the major ore of lead. Based on the ESRT Properties of Common Minerals, which mineral is it?

Worked solution
$\text{Use the most limiting clues: metallic luster, } H \approx 2.5$ Start with hardness and luster to narrow the chart.
$\text{cubic cleavage} + \text{ore of lead} \Rightarrow \text{Galena (PbS)}$
Answer: Galena

Minerals are identified by a combination of physical properties; galena's low hardness, cubic cleavage, metallic luster, and use as the lead ore uniquely match the ESRT chart.

Question 34 · 2 pts

An igneous rock is light colored with coarse, intergrown crystals $1$ to $10$ mm across and is composed mainly of quartz and potassium feldspar. Using the Scheme for Igneous Rock Identification, the rock is most likely

Worked solution
$\text{coarse crystals (1 to 10 mm)} \Rightarrow \text{intrusive, slow cooling}$
$\text{light color} + \text{quartz} + \text{K-feldspar} \Rightarrow \text{felsic (granitic)}$
$\text{coarse} + \text{felsic} \Rightarrow \text{Granite}$
Answer: Granite

In the igneous scheme, crystal size records cooling rate (coarse means slow, intrusive) and mineral makeup records composition (quartz plus K-feldspar means felsic), which together identify granite.

Question 44 · 2 pts

Rock salt and rock gypsum are sedimentary rocks. According to the Scheme for Sedimentary Rock Identification, these rocks form primarily by which process?

Worked solution
$\text{Rock salt (halite) and rock gypsum are chemically formed evaporites.}$
$\text{As water evaporates, dissolved minerals become concentrated, precipitate, and crystallize.}$
Answer: Evaporation of water, causing dissolved minerals to precipitate and crystallize

Chemically formed sedimentary rocks such as rock salt ($NaCl$) and rock gypsum precipitate and crystallize as mineral-rich water evaporates.

Question 48 · 2 pts

A mineral with a metallic luster looks silvery-gray to black, but when rubbed on a streak plate it leaves a reddish-brown streak. The sample is not attracted to a magnet. Using the Properties of Common Minerals chart, which mineral is it?

Worked solution
$\text{Streak, the color of the powdered mineral, is more reliable than surface color.}$
$\text{A reddish-brown streak identifies hematite, even when the sample looks gray or black.}$
$\text{Not being magnetic rules out magnetite, which has a black streak and is magnetic.}$
Answer: Hematite

Streak, the color of a mineral's powder, is a more reliable diagnostic property than surface color, and hematite always leaves a reddish-brown streak.

Question 5 · 2 pts

A sedimentary rock deep within Earth's crust is subjected to intense heat and pressure. Its mineral grains recrystallize into new, aligned crystals, but the rock does not melt. Which type of rock is formed by this process?

Worked solution
$Metamorphic rocks form when existing rock is changed by heat and/or pressure while remaining solid (no melting occurs).$ This distinguishes metamorphism from igneous processes.
$Igneous rock instead requires melting of material into magma or lava and subsequent cooling and solidification, which did not occur here.$
$Since the original sedimentary rock recrystallized without melting, the result is a metamorphic rock.$
Answer: Metamorphic rock

Recrystallization of existing rock under heat and pressure without melting is the defining process that produces metamorphic rock, as opposed to the melting and cooling that forms igneous rock.

Question 41 · 2 pts

Which process is directly responsible for the formation of igneous rock?

Worked solution
$\text{Magma/lava cools} \rightarrow \text{minerals crystallize} \rightarrow \text{igneous rock}$
Answer: Crystallization (solidification) of molten magma or lava

Igneous rocks form specifically when molten material (magma below the surface or lava at the surface) cools and its minerals crystallize into an interlocking solid; the other choices describe sedimentary or metamorphic processes.

Question 54 · 4 pts · constructed response

Describe one process by which a sedimentary rock, such as shale, can be transformed into a metamorphic rock, such as slate. In your answer, identify the agent(s) responsible for this change and the specific physical change that occurs in the rock.

Model answer: Shale is transformed into slate through metamorphism, in which heat and pressure deep within Earth's crust act on the shale without melting it. This causes the platy minerals in the rock to recrystallize and become aligned in parallel layers, producing the foliation (banding) and increased density that distinguish slate from shale.
Worked solution
$Identify starting rock type: shale is a sedimentary rock formed from compacted clay/mud particles.$ Reasoning step
$Identify agents of change: heat and pressure (without melting) applied during burial/mountain building cause metamorphism.$
$Identify the resulting physical change: minerals recrystallize and align into parallel layers, creating foliation and increasing rock density.$
Answer: Shale is transformed into slate through metamorphism, in which heat and pressure deep within Earth's crust act on the shale without melting it. This causes the platy minerals in the rock to recrystallize and become aligned in parallel layers, producing the foliation (banding) and increased density that distinguish slate from shale.

The rock cycle shows that any rock type can become a metamorphic rock when subjected to heat and/or pressure without melting; in the case of shale becoming slate, this causes recrystallization and alignment of minerals into the foliated texture characteristic of slate.

Question 61 · 4 pts · constructed response

A mineral sample has a hardness of about $6$, a black streak, a metallic to submetallic luster, and breaks with an irregular fracture rather than smooth cleavage planes. It is also strongly attracted to a magnet. Identify this mineral and explain which two properties were most useful in determining its identity.

Model answer: The mineral is magnetite. Its black streak combined with strong magnetism are the most diagnostic properties, since magnetite is the only common rock-forming mineral that is strongly magnetic.
Worked solution
$Hardness about 6 and metallic luster narrow the choices to a small group of metallic minerals such as magnetite, pyrite, and galena.$
$Pyrite has a greenish-black streak and is not magnetic; galena has a hardness near 2.5 and is not magnetic.$
$Strong magnetism together with a black streak match magnetite uniquely.$
Answer: The mineral is magnetite. Its black streak combined with strong magnetism are the most diagnostic properties, since magnetite is the only common rock-forming mineral that is strongly magnetic.

Streak and special properties such as magnetism are more diagnostic than luster or hardness alone because several minerals can share similar hardness and luster values; magnetite is identified reliably by its unique magnetic property.

Question 71 · 4 pts · constructed response

A rock sample is made up entirely of large, visible, interlocking crystals of quartz, feldspar, and mica. Field evidence shows this rock formed from magma that cooled slowly far below Earth's surface. Classify this rock as igneous, sedimentary, or metamorphic, and state whether it is intrusive or extrusive. Explain the reasoning behind your classification.

Model answer: The rock is igneous and intrusive.
Worked solution
$The rock formed directly from the cooling and solidification of magma, which is the definition of an igneous rock.$
$Magma that cools slowly below Earth's surface allows large, well-formed, interlocking crystals to grow, whereas rapid cooling at the surface produces small or glassy crystals.$
$Because cooling occurred slowly below the surface, the rock is classified as intrusive igneous rock.$
Answer: The rock is igneous and intrusive.

Crystal size in igneous rock reflects cooling rate: slow cooling deep underground gives minerals time to grow into large, interlocking crystals, which is the identifying feature of intrusive igneous rocks such as granite.

Question 77 · 4 pts · constructed response

Limestone, a sedimentary rock composed mainly of the mineral calcite, is buried deep within Earth's crust where it is subjected to high temperature and pressure but does not melt. Identify the rock that forms as a result of this process, describe the change that produces it, and explain why this process is classified as metamorphism rather than the formation of an igneous rock.

Model answer: Marble forms. It forms when calcite crystals in limestone recrystallize into larger, interlocking crystals under heat and pressure while remaining solid. This is classified as metamorphism, not igneous rock formation, because igneous rocks form specifically from the cooling and solidification of molten magma or lava, whereas marble forms without the rock ever melting.
Worked solution
$Starting rock: limestone (sedimentary, calcite-rich)$
$Heat and pressure applied, temperature stays below the melting point$
$Calcite crystals recrystallize into larger interlocking crystals$
$Resulting rock: marble (metamorphic)$
$No melting occurred, so this is metamorphism rather than igneous rock formation$
Answer: Marble forms. It forms when calcite crystals in limestone recrystallize into larger, interlocking crystals under heat and pressure while remaining solid. This is classified as metamorphism, not igneous rock formation, because igneous rocks form specifically from the cooling and solidification of molten magma or lava, whereas marble forms without the rock ever melting.

Metamorphic rocks form when an existing rock's mineral structure and texture change under heat and/or pressure while the rock remains solid; limestone recrystallizes into marble without melting, distinguishing it from igneous processes.

Question 5 · 2 pts

Which rock forms directly from the cooling and solidification of molten material?

Worked solution
$\text{Sedimentary rock forms from compaction/cementation of sediments, not from melting.}$
$\text{Metamorphic rock forms when existing rock is changed by heat and pressure without melting.}$
$\text{Igneous rock forms when magma or lava cools and solidifies.}$
Answer: Igneous rock

According to the rock cycle, igneous rocks are the only rock type that forms directly from the cooling and crystallization of molten magma or lava, whether underground (intrusive) or at the surface (extrusive).

Question 19 · 2 pts

Two mineral samples both appear black and shiny on their surfaces. When each sample is rubbed across an unglazed porcelain streak plate, one leaves a reddish-brown powder mark and the other leaves a black powder mark. Which mineral property was used to help distinguish these two samples?

Worked solution
$Streak is the color of a mineral's powder, obtained by rubbing the mineral across an unglazed streak plate.$
$Streak color is more reliable for identification than surface color because surface color can be altered by weathering or impurities, while powdered streak color is more consistent for a given mineral.$
$Since the two black, shiny minerals produced different streak colors (reddish-brown versus black), streak was the property used to tell them apart.$
Answer: Streak

Streak reveals a mineral's true color in powdered form and is especially useful for identifying minerals, such as hematite (reddish-brown streak) versus magnetite (black streak), that can otherwise look identical on the surface.

Question 27 · 2 pts

Magma that cools slowly beneath Earth's surface forms an igneous rock with large, well-formed mineral crystals that are visible to the naked eye. Which rock is an example of this type of intrusive igneous rock?

Worked solution
$Slow cooling beneath the surface allows large crystals to grow, producing a coarse-grained texture.$
$Granite is a light-colored, coarse-grained intrusive igneous rock formed exactly this way.$
$Basalt is extrusive and fine-grained, shale is sedimentary, and gneiss is metamorphic with banding, so none fit the description.$
Answer: Granite

Slow cooling of magma at depth produces coarse crystals; granite is the standard Regents example of an intrusive igneous rock with this texture.

Question 41 · 2 pts

According to the rock cycle, which process directly forms an igneous rock?

Worked solution
$Igneous rocks form specifically from the cooling and crystallization of molten rock material.$
$Magma that cools slowly below Earth's surface forms intrusive igneous rock with large crystals.$
$Lava that cools quickly at the surface forms extrusive igneous rock with small or no crystals.$
$Compaction/cementation forms sedimentary rock, and heat/pressure without melting forms metamorphic rock, so those are eliminated.$
Answer: cooling and solidification (crystallization) of molten magma or lava

Igneous rocks are defined by their origin: they crystallize directly from cooling magma (underground) or lava (at the surface), distinguishing them from sedimentary rock (compaction/cementation) and metamorphic rock (heat and pressure without melting).

Question 55 · 4 pts · constructed response

A rock sample is composed of visible, interlocking crystals of quartz, feldspar, and mica of roughly equal size, with no layering or banding present. State the rock's origin (igneous, sedimentary, or metamorphic) and identify whether it most likely formed from slow cooling of magma at depth or rapid cooling of lava at the surface. Explain your reasoning using the texture described.

Model answer: The rock is igneous, and it formed from slow cooling of magma at depth (intrusive/plutonic origin), because it has large, visible interlocking crystals rather than a fine-grained or glassy texture.
Worked solution
$\text{Texture: large, visible, interlocking crystals}$ No layering, banding, or fossils, ruling out sedimentary and foliated metamorphic rocks
$\text{Large crystal size indicates slow cooling}$ Slow cooling underground allows more time for large crystals to grow
$\text{Conclusion: igneous rock, intrusive origin (cooled slowly at depth)}$
Answer: The rock is igneous, and it formed from slow cooling of magma at depth (intrusive/plutonic origin), because it has large, visible interlocking crystals rather than a fine-grained or glassy texture.

Crystal size in igneous rocks is controlled by cooling rate; large, visible interlocking crystals with no banding indicate slow cooling of magma below Earth's surface (intrusive/plutonic rock), as opposed to the small or glassy crystals produced by rapid cooling of lava at the surface.

Question 60 · 4 pts · constructed response

A sedimentary rock sample is made of rounded pebbles, 3 to 10 millimeters in diameter, that have been compacted and cemented together with smaller sand-sized grains filling the spaces between the pebbles. (a) Identify this sedimentary rock. (b) Name two processes by which loose sediment becomes a solid sedimentary rock. (c) Explain what the rounded shape of the pebbles indicates about how they were transported before becoming part of this rock.

Model answer: The rock is conglomerate. It formed through compaction (pressure from overlying sediment squeezes grains together) and cementation (dissolved minerals precipitate and bind the grains together). The rounded shape of the pebbles indicates that they were abraded (worn down and smoothed) during a long period or long distance of transport, most likely by moving water.
Worked solution
$Sediment made of rounded, pebble-sized (larger than 2 mm) particles cemented together is classified as conglomerate.$
$Lithification of sediment into rock occurs mainly through compaction and cementation.$
$Rounded grains result from abrasion during transport; the more rounded the grains, the longer the transport distance/time.$
Answer: The rock is conglomerate. It formed through compaction (pressure from overlying sediment squeezes grains together) and cementation (dissolved minerals precipitate and bind the grains together). The rounded shape of the pebbles indicates that they were abraded (worn down and smoothed) during a long period or long distance of transport, most likely by moving water.

Conglomerate is a clastic sedimentary rock composed of rounded, pebble-sized fragments; rounding of the clasts reflects extensive abrasion during transport, and the rock forms once compaction and cementation lithify the loose sediment.

Question 68 · 4 pts · constructed response

A rock sample is light-colored, composed mainly of quartz and feldspar, and has large, interlocking mineral crystals that are easily seen and identified without magnification. The rock shows no layering, no fossils, and no banding. Identify whether this rock is igneous, sedimentary, or metamorphic. Name one specific rock that fits this description, and describe the cooling conditions that produced its coarse crystal texture.

Model answer: The rock is igneous; a specific example is granite. Its large, interlocking crystals formed because magma cooled very slowly deep beneath Earth's surface (intrusive/plutonic cooling), giving mineral crystals a long time to grow to a visible size.
Worked solution
$Light color plus quartz and feldspar with no layering or fossils rules out sedimentary rock.$
$No banding or foliation rules out metamorphic rock.$
$Large, visible interlocking crystals indicate an intrusive igneous texture, identifying the rock as igneous (example: granite).$
$Slow cooling underground allows atoms more time to arrange into large crystals, producing the coarse-grained texture.$
Answer: The rock is igneous; a specific example is granite. Its large, interlocking crystals formed because magma cooled very slowly deep beneath Earth's surface (intrusive/plutonic cooling), giving mineral crystals a long time to grow to a visible size.

Crystal size in igneous rocks directly reflects cooling rate: rocks that cool slowly below the surface (intrusive) form large, visible crystals like those in granite, while rocks that cool quickly at the surface form small or no crystals.

Question 18 · 2 pts

Which process directly forms sedimentary rock from loose, unconsolidated sediment?

Worked solution
$Melting and rapid cooling describe the formation of igneous rock, not sedimentary rock.$
$Crystallization from magma also describes igneous rock formation.$
$Recrystallization under heat and pressure describes metamorphic rock formation.$
$Loose sediment becomes sedimentary rock when it is compacted (squeezed together) and cemented (minerals precipitate to bind grains), forming clastic sedimentary rock such as sandstone or shale.$
Answer: Compaction and cementation

According to the rock cycle, sediment is converted into sedimentary rock through the combined processes of compaction and cementation, which is distinct from the melting/cooling of igneous rock or the heat/pressure recrystallization of metamorphic rock.

Question 30 · 2 pts

A rock sample is made of interlocking mineral crystals too small to see without magnification, and laboratory tests show its overall chemical composition matches that of granite. Which process most likely formed this rock?

Worked solution
$Crystal size in an igneous rock reflects how quickly the melt cooled.$
$Very fine (microscopic) crystals indicate rapid cooling, which occurs when lava cools quickly at or near Earth's surface.$
$Because the composition matches granite (a felsic rock), the fine-grained equivalent formed at the surface is rhyolite, an extrusive igneous rock.$
Answer: Rapid cooling of lava at Earth's surface

Texture in igneous rocks records cooling rate: coarse crystals form from slow cooling underground, while fine or microscopic crystals form from rapid cooling of lava exposed at Earth's surface, so a fine-grained rock with granite's composition is extrusive rather than intrusive.

Question 69 · 4 pts · constructed response

A sample of igneous rock contains large, well-formed, interlocking mineral crystals that are easily seen with the naked eye. State whether this rock most likely cooled at Earth's surface or deep beneath the surface, and explain the relationship between cooling rate and crystal size that supports your answer.

Model answer: The rock cooled slowly, deep beneath Earth's surface (it is an intrusive igneous rock).
Worked solution
$\text{Large, well-formed crystals indicate slow cooling of magma.}$
$\text{Slow cooling occurs underground, where the rock is insulated by surrounding material.}$
$\text{Therefore the rock is intrusive igneous rock, formed below Earth's surface.}$
Answer: The rock cooled slowly, deep beneath Earth's surface (it is an intrusive igneous rock).

Crystal size in igneous rocks is inversely related to cooling rate: magma that cools slowly underground forms large, visible crystals, while lava that cools quickly at the surface forms small or no crystals.

Question 77 · 4 pts · constructed response

A rock sample is composed entirely of large, easily visible, interlocking crystals of quartz, potassium feldspar, and mica. The rock shows no layering, banding, or foliation. State the name of this rock, identify whether it is igneous, sedimentary, or metamorphic, and describe the cooling process that produced its crystal texture.

Model answer: The rock is granite, an intrusive (plutonic) igneous rock. Its large interlocking crystals formed because magma cooled slowly beneath Earth's surface, giving mineral crystals enough time to grow to a visible, coarse-grained size.
Worked solution
$\text{Composition: quartz + feldspar + mica} \rightarrow \text{granitic mineral family}$ Match mineral composition to rock type
$\text{Large, visible crystals} \rightarrow \text{coarse-grained texture}$ Large crystals indicate slow cooling
$\text{Slow cooling occurs underground} \rightarrow \text{intrusive igneous origin}$ Classify origin
Answer: The rock is granite, an intrusive (plutonic) igneous rock. Its large interlocking crystals formed because magma cooled slowly beneath Earth's surface, giving mineral crystals enough time to grow to a visible, coarse-grained size.

Crystal size in igneous rocks depends directly on cooling rate: slow cooling deep underground allows large, interlocking crystals to form, producing coarse-grained intrusive rocks like granite, in contrast to fine-grained rocks that cool quickly at the surface.

Question 14 · 1 pt

A rock shows visible layers (banding) of light and dark minerals and is made of interlocking crystals. This rock is best classified as

Worked solution
$\text{banding} + \text{crystals} \Rightarrow \text{metamorphic}$ Foliation is a metamorphic texture.
Answer: \text{metamorphic}

Banding (foliation) of aligned crystals forms under heat and pressure, the signature of metamorphic rock like gneiss.

Question 35 · 2 pts

According to the Scheme for Igneous Rock Identification, density increases as composition changes from felsic (granitic) to mafic (gabbroic). Which of these igneous rocks has the greatest density?

Worked solution
$\text{felsic} \approx 2.7\ \text{g/cm}^3, \quad \text{mafic} \approx 3.0\ \text{g/cm}^3$
$\text{gabbro is mafic} \Rightarrow \text{greatest density} \approx 3.0\ \text{g/cm}^3$
Answer: Gabbro

Density of igneous rocks depends on composition, not texture; mafic rocks like gabbro contain denser, iron- and magnesium-rich minerals, giving the highest density of about 3.0 g/cm³.

Question 36 · 2 pts

A sedimentary rock is made of rounded pebbles larger than $0.2$ cm cemented in a finer matrix. Using the Scheme for Sedimentary Rock Identification, this rock is

Worked solution
$\text{grain size} > 0.2\ \text{cm} \Rightarrow \text{pebble (gravel) sized clasts}$
$\text{rounded clasts} \Rightarrow \text{Conglomerate} \;(\text{angular} \Rightarrow \text{Breccia})$
Answer: Conglomerate

Clastic sedimentary rocks are classified by grain size and shape; pebble-sized rounded fragments cemented together form conglomerate, while angular fragments form breccia.

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