Depositional environment of rock salt

EARTH SCIENCE LAB

Sedimentary Rocks

For this lab, you will be making observations and interpretations about sedimentary rocks. I

recommend that you print the data table provided and fill it in as you analyze each sample.

Then, use your table to answer the questions at the end of the lab. Also answer these questions on

our online class site so that you can get credit for the laboratory exercise.

Sediment and Sedimentary Rocks

Sedimentary Rocks formed by the consolidation of sediment. The word sediment comes from the

Latin word sedere, meaning “to settle.” Sediments are solid materials that settle from a state of

suspension or solution in a fluid. For example, take sediment in a lake. Sediment can be an

accumulation of sand that has settled to the bottom of the lake. However, sediment can also be

salt that was at first dissolved in the water but is now precipitating out of that solution and is

settling to the bottom of the lake. These two types of sediment can be lithified (converted into

sedimentary rock) as different types of sedimentary rocks. Therefore, there are two main types of

sedimentary rock, clastic sedimentary rocks and chemical sedimentary rocks.

Clastic Sedimentary Rocks

Clastic sedimentary rocks are composed of fragments of older rocks. Therefore, their formation

begins with weathering. Mechanical weathering breaks down rock into smaller particles of

sediment. Chemical weathering can decompose minerals (example: feldspars to clays). Now that

the original rock was weathered, erosion removes the grains from that location to a new location.

The grains of sediment get transported and eventually deposited, or set down. Over time, they get

buried by younger sediment. The pressure of overlying material causes compaction of the

sediment. Fluids passing through the buried sediment may precipitate minerals in the pore spaces

between grains leading to cementation. Therefore, lithification has begun, which is the process of

converting sediments into sedimentary rock, which involves compaction and cementation.

The texture and composition of clastic sedimentary rocks help us to make interpretations about

the formation of these rocks as well as the environment in which they formed. Textural details

that help us to interpret clastic sedimentary rocks are grain size, sorting, and grain shape.

Grain size is simply a measurement of how large the grains are in a sedimentary rock. In order,

from largest to smallest, grain sizes include: boulders, cobbles, pebbles, granules, sand, silt, and

clay. Each of these terms has a specific size requirement, noted below.

Boulders greater than 256 mm

Cobbles 64 mm to 256 mm

Pebbles 4 mm 64 mm

Granules 2 mm to 4mm

Sand 1/16 mm to 2 mm

Silt 1/256 mm to 1/16 mm

Clay less than 1/256 mm

Analyzing the grain sizes of the sediment in a rock is important because grain size reflects the

strength of the process that transported the grains. For example, boulders can only be transported

by rivers during flood stages, mudflows, mass wasting (landslides), or some other high-energy

process. Therefore, if a layer of sedimentary rock has boulders in it, you know that it was

deposited during a time of flooding, or some other high energy environment. Another example is

a layer of sedimentary rock that has a lot of silt and clay in it. Silt and clay will not be deposited

in swift flowing rivers, since. Instead, they are deposited in low-energy environments where

water is rather still, allowing the grains to settle out of the water.

Sorting describes the distribution of grain sizes, meaning how similar the grains are in size to

each other. Sorting is described as being either very well sorted, well sorted, poorly sorted or

very poorly sorted. If all of the grains have the same size, it is very well-sorted. If most of the

grains are similar in size, it is well sorted. If grains are a variety of grain sizes, it is poorly-sorted.

If grains vary greatly in size, it is very poorly sorted. Sorting is important because it reflects if

the transport process was able to sort the sediment according to its grain size. It tells you whether

or not the sediment has been reworked after deposition. For example, waves rework sediments,

concentrating grains of the same size at the beach, producing well-sorted sediment. Another

example would be a debris flow, which deposits sediment rapidly with little to no reworking,

producing poorly-sorted sediment.

Grain shape refers to how smooth the grains of sediment are. It is described as being angular,

subangular, subrounded, and rounded. Grains that have sharp or rough corners are angular.

Grains that have smooth surfaces are rounded. Shape is important because it is used to determine

the distance of transport. Rough edges get ground down and smoothed as they bump into other

grains during transport or reworking. Therefore, the more smooth and rounded the grains, the

further the grains have been transported from where they started. For this lab, if a rock is made of

fine-grained sediment such as silt or clay, we will assume that the grains are rounded.

Mineralogy is also important in determining the source of the sediment, as well as the

environment and the distance of transport. Quartz is the most common mineral in sedimentary

rocks because it is hard, has no cleavage, and has a low temperature of formation. Therefore,

quartz survives long, turbulent trips better than most minerals. If a rock contains an abundance of

quartz, and not many other minerals, this means that it has probably survived multiple

weathering events and trips, when all other minerals have not.

Clastic sedimentary rocks are classified primarily by grain size. Figure 1 contains common

sedimentary rocks. Notice that they are named due to the size of the sediment. For example, if it

is made of sand, it is called sandstone. If it is made of silt, it is a siltstone. If it is made of clay, it

is a claystone. However, if it is made of silt or clay and is fissile (breaks in flat planes), it is

called shale. If it is made of grains larger than sand, there are only two options; it is either a

conglomerate or a breccia, depending on if the grains are round or angular. If they are more

rounded, the rock is a conglomerate. If the grains are more angular, it is a breccia.

Figure 1. Clastic Sedimentary Rocks

Grain Size Grain Name Distinctive Features Depositional Environment Rock Name

Greater than

4mm

Boulders, cobbles,

pebbles, and/or

granules

Angular grains in finer sediment that

surround them (poorly sorted)

High energy environments. Product

of mass wasting processes such as

rockslides, mud and debris flows,

rockfalls, etc.

Breccia

Greater than

2 mm

Boulders, cobbles,

pebbles, and/or

granules

Rounded grains in finer sediment that

surrounds them (poorly sorted)

High energy environment, such as

rivers, ocean shorelines, and alluvial

fans.

Conglomerate

1/16 mm to 2

mm Sand

Can be well-sorted to poorly-sorted;

well-rounded to angular; composition

often includes various amounts of

quartz, feldspars, biotite, hornblende,

etc.

Well-sorted sandstones form on

beaches, windblown sand dunes,

continental shelves. Moderately-

sorted sandstones form in rivers,

deltas, alluvial fans. Very poorly-

sorted sandstones form from debris

flows or underwater slumps.

Sandstone

1/256 mm to

1/16 mm Silt

Can’t see grains with naked eye. Not

layered. Does not stick to tongue, but

instead feels gritty when chewed.

Form in low energy environments

such as lakes, deeper parts of ocean,

floodplains of river channels

Siltstone

less than

1/256 mm Clay

Can’t see grains with naked eye. Not

layered. Sticks to tongue and feels

sticky when chewed.

Form in very low energy

environments such as outer parts of

deltas or floodplains, deep lake, deep

ocean floor, etc.

Claystone

Up to 1/16

mm Silt or clay

Can’t see grains with naked eye. Has a

finely laminated/layered structure that

allows it to split along planes (fissile).

Low to very low energy

environments. Silt: lakes, deeper

parts of ocean, floodplains of river

channels. Clay: outer parts of deltas

or floodplains, deep lake, deep ocean

floor, etc.

Shale

Chemical Sedimentary Rocks

Chemical sedimentary rocks are formed when minerals precipitate from ions dissolved in water.

Biochemical rocks are subgroup of chemical sedimentary rocks that are an accumulation of organic

debris.

Naming chemical sedimentary rocks is done mostly on the basis of the mineral that was being

precipitated out of the water. For example, if gypsum is precipitated out, settling to the bottom of the

water, a sedimentary rock called rock gypsum will form. You can test for gypsum because the rock will

scratch easily with a fingernail, since gypsum only has a hardness of two. If halite is precipitated out of

the water, rock halite or rock salt will form. You can test for halite by licking the rock. If it tastes salty, it

is halite. Rocks that form from calcium carbonate (calcite) precipitating out of the water are collectively

called limestone. You can test for limestone by dropping hydrochloric acid (HCl) on it. If it fizzes in

acid, it contains calcite, and is limestone. There are many types of limestones, depending on the different

forms the calcite takes as it is coming out of solution. Many organisms use calcium (Ca) carbonate

(CO3 2-

) dissolved in sea or lake water to make their shells. When they die, their shells accumulate to

make limestone. For example, if the limestone is made entirely of coarse shell fragments that have

accumulated, it is called coquina. If the limestone has an abundance of fossils surrounded in fine-grained

limestone mud, it is called fossiliferous limestone. If the limestone is fine-grained and is either made of

almost microscopic organisms with calcite shells and skeletons, or just precipitated out as soft

(powdery), fine-grained calcite, it is called chalk. If the limestone is made of ooids (spherical or “egg

shaped” grains composed of concentric layers of calcium carbonate), it is called oolitic limestone. If the

limestone lacks all of these above distinctive features, it is micrite, or is often just called limestone.

Occasionally, some of the calcium in limestone can be replaced by magnesium as magnesium-rich water

flows through an area. If this happens, the calcite in the limestone changes to dolomite, a calcium-

magnesium-carbonate mineral. A rock made of the mineral dolomite is called dolostone. You can tell if

the rock is dolostone if it no longer fizzes in acid, unless it is scratched first, producing a powder that

will fizz in acid.

As a reminder, if life is involved with helping to produce a chemical sedimentary rock, it can also be

called a biochemical sedimentary rock. For example, any of the limestones that contained shells or

skeletons would be biochemical. Another biochemical sedimentary rock is coal. Coal forms by

accumulation and compaction of plant debris. It forms in swamps and bogs where there is so much

organic material that there is not enough oxygen for all of it to decay, turning it to coal. There are

several stages or grades of coal, due to increasing temperature and pressure, which increases the carbon

content, and decreases the moisture. Stages of coal include peat, lignite, bituminous, and anthracite

(although anthracite is actually considered a metamorphic rock). Peat is typically brown and crumbly

and has visible, unconsolidated plant remains. Lignite is soft and brownish-black, and is produced when

peat is buried at shallow depths. Bituminous Coal is black, and is harder and shinier than lignite, as it

was buried deeper than lignite. Anthracite Coal is buried deeper than bituminous coal and is therefore

harder, denser, and shinier than bituminous coal. However, anthracite will not be seen in this lab, as it is

considered a metamorphic rock.

Use Figure 2 to help you classify chemical and biochemical sedimentary rocks. First, determine what

mineral or material is present. If it fizzes in acid, it has calcite and is a type of limestone. If this is the

case, look for other textures that would help you to figure out a more specific name for that type of

limestone.

Figure 2. Chemical and Biochemical Sedimentary Rocks

Main Mineral

or Material Distinctive Features Depositional Environment Rock Name

Gypsum Hardness of 2, easily scratched with fingernail,

no reaction to HCl (hydrochloric acid)

Sites with high evaporation, desert

“dry” lakes, ocean margins Rock Gypsum

Halite No reaction to HCl, tastes salty, is not

scratched with fingernail

Sites with high evaporation, desert

“dry” lakes, ocean margins Rock Halite/Rock Salt

Calcite

Fizzes with HCl, fine-grained, typically looks

like mud with no distinctive features other than

occasional subconchoidal fracture

Shallow oceans Micrite/limestone

Calcite Fizzes with HCl, made of coarse shell

fragments Shallow oceans Coquina

Calcite

Fizzes with HCl, contains obvious fossils of

clams, snails, etc. in a matrix of fine grained

calcite rich mud

Shallow oceans Fossiliferous Limestone

Calcite

Fizzes with HCl, soft (often powdery), fine-

grained, often composed of fine-grained shells

and skeletons of microorganisms.

Shallow oceans Chalk

Calcite

Fizzes with HCl, contains ooids (spherical or

“egg shaped” grains composed of concentric

layers of calcium carbonate)

Shallow oceans with warm water near

the equator. Oolitic Limestone

Dolomite Only fizzes with HCl when powdered Shallow oceans. Later, water rich in

magnesium came through the area. Dolostone

Plant material Unconsolidated plant remains still visible.

Brown and crumbly. Swamps or bogs Peat

Plant material Plant remains not visible. Soft and brownish-

black. Beginning to look a little shiny. Swamps or bogs Lignite

Plant material Plant remains not visible. Black, harder and

shinier than lignite. Swamps or bogs Bituminous Coal

Figure 3. Data table for observations of sedimentary rocks.

Sample #

Which one: clastic or chemical? (Think: did it

form from broken up rock and is therefore clastic, or

did it precipitate out as crystalline material out of the water and is therefore

chemical? Of course, if it is a coal, it is accumulated

plant debris though.)

If clastic, what size are the

grains? (boulders, cobbles, pebbles,

granules, sand, silt, or clay)

If clastic, describe the sorting of the grains (very

poorly sorted, poorly sorted, well sorted, very well

sorted).

If clastic, describe the shape of the

grains (angular, subangular,

subrounded,or rounded).

If chemical (or biochemical),

what mineral does it mostly contain?

What is a possible depositional

environment for this rock?

Rock Name

1

2

3

4

5

6

7

8

9

10

Sample #

Which one: clastic or chemical? (Think: did it

form from broken up rock and is therefore clastic, or

did it precipitate out as crystalline material out of the water and is therefore

chemical? Of course, if it is a coal, it is accumulated

plant debris though.)

If clastic, what size are the

grains? (boulders, cobbles, pebbles,

granules, sand, silt, or clay)

If clastic, describe the sorting of the grains (very

poorly sorted, poorly sorted, well sorted, very well

sorted).

If clastic, describe the shape of the

grains (angular, subangular,

subrounded,or rounded).

If chemical (or biochemical),

what mineral does it mostly contain?

What is a possible depositional

environment for this rock?

Rock Name

11

12

13

14

15

16

17

18

19

20

Observe each of the images of samples of sedimentary rocks in Figure 4. Record your observations for

appropriate textures and composition in the data table provided in Figure 3. Many of the boxes will be

left blank, as some boxes will not apply to each sample. Use Figure 1 to help you classify clastic

sedimentary rocks and Figure 2 to help you classify chemical and biochemical sedimentary rocks.

Figure 4. Samples of Sedimentary Rocks (for scale, assume that each sample is actual size).

Sample #1 Full View Sample #1 Close Up (Notice that it fizzes in HCl)

Sample #2 Full View

Sample #2 Close Up (Notice that it fizzes in HCl)

Sample #3 Full View Sample #3 Close Up

Sample #4 Full View

Sample #4 Close Up (If you were to lick it, this

would taste salty)

Sample #5 Full View Sample #5 Close Up

Sample #6 Full View Sample #6 Close Up

Sample #7 Full View

Sample #7 Close Up (This sample scratches easily

with a fingernail)

Sample #8 Full View Sample #8 Close Up

Sample #9 Full View Sample #9 Close Up

Sample #10 Full View Sample #10 Close Up (Notice that it fizzes in HCl)

Sample #11 Full View

Sample #11 Close Up (If you licked it, your tongue

would stick to it.)

Sample #12 Full View Sample #12 Close Up

Sample #13 Full View

Sample #13 Close Up

Sample #14 Full View

Sample #14 Close Up (If you licked it, your tongue

would stick to it.)

Sample #15 Full View Sample #15 Close Up (Notice that it only fizzes in

HCl when it is scratched first.)

Sample #16 Full View Sample #16 Close Up (Notice that it fizzes in HCl)

Sample #17 Full View

Sample #17 Close Up (This would not stick to your

tongue, but would instead feel gritty in your mouth)

Sample #18 Full View Sample #18 Close Up (Notice that it fizzes in HCl)

Sample #19 Full View Sample #19 Close Up

Sample #20 Full View

Sample #20 Close Up (If you licked it, your tongue

would stick to it.)

Answer the questions below. You will use your completed data table to answer most of these questions,

so you could just skip this part and use your completed data table to answer the same questions online.

1. Sample #1: Is this rock clastic or chemical?

A. clastic B. chemical

2. Sample #1: What mineral or material does this rock mostly contain?

A. gypsum B. halite C. calcite D. dolomite E. plant material

3. Sample #1: What is a possible depositional environment for this rock?

A. area that experienced mass wasting such as rockslides, mud and debris flows, rockfalls, etc. B. rivers, ocean shorelines, and alluvial fans C. beaches, windblown sand dunes, continental shelves, rivers, deltas, alluvial fans, debris flows or

underwater slumps

D. lake, deeper part of ocean, floodplain of river channel E. outer parts of deltas or floodplains, deep lake, deep ocean floor, etc. F. dry lake G. shallow ocean H. swamp or bog

4. Sample #1: What is the name of this rock?

A. breccia B. conglomerate C. sandstone D. siltstone E. claystone F. shale G. rock gypsum H. rock halite/rock salt I. micrite/limestone J. coquina K. fossiliferous limestone L. chalk M. oolitic limestone N. dolostone O. peat P. lignite Q. bituminous coal

5. Sample #2: Is this rock clastic or chemical?

A. clastic B. chemical

6. Sample #2: What mineral or material does this rock mostly contain?

A. gypsum B. halite C. calcite D. dolomite E. plant material

7. Sample #2: What is a possible depositional environment for this rock?

A. area that experienced mass wasting such as rockslides, mud and debris flows, rockfalls, etc. B. rivers, ocean shorelines, and alluvial fans C. beaches, windblown sand dunes, continental shelves, rivers, deltas, alluvial fans, debris flows or

underwater slumps

D. lake, deeper part of ocean, floodplain of river channel E. outer parts of deltas or floodplains, deep lake, deep ocean floor, etc. F. dry lake G. shallow ocean H. swamp or bog

8. Sample #2: What is the name of this rock?

A. breccia B. conglomerate C. sandstone D. siltstone E. claystone F. shale G. rock gypsum H. rock halite/rock salt I. micrite/limestone J. coquina K. fossiliferous limestone L. chalk M. oolitic limestone N. dolostone O. peat P. lignite Q. bituminous coal

9. Sample #3: Is this rock clastic or chemical?

A. clastic B. chemical

10. Sample #3: What size are the grains?

A. boulders

B. cobbles C. pebbles D. granules E. sand F. silt G. clay

11. Sample #3: Describe the sorting of the grains.

A. very poorly sorted/poorly sorted B. well sorted/very well sorted

12. Sample #3: describe the shape of the grains.

A. angular/subangular B. subrounded/rounded

13. Sample #3: What is a possible depositional environment for this rock?

A. area that experienced mass wasting such as rockslides, mud and debris flows, rockfalls, etc. B. rivers, ocean shorelines, and alluvial fans C. beaches, windblown sand dunes, continental shelves, rivers, deltas, alluvial fans, debris flows or

underwater slumps

D. lake, deeper part of ocean, floodplain of river channel E. outer parts of deltas or floodplains, deep lake, deep ocean floor, etc. F. dry lake G. shallow ocean H. swamp or bog

14. Sample #3: What is the name of this rock?

A. breccia B. conglomerate C. sandstone D. siltstone E. claystone F. shale G. rock gypsum H. rock halite/rock salt I. micrite/limestone J. coquina K. fossiliferous limestone L. chalk M. oolitic limestone N. dolostone O. peat P. lignite Q. bituminous coal

15. Sample #4: Is this rock clastic or chemical?

A. clastic B. chemical

16. Sample #4: What mineral or material does this rock mostly contain?

A. gypsum B. halite C. calcite D. dolomite E. plant material

17. Sample #4: What is a possible depositional environment for this rock?

A. area that experienced mass wasting such as rockslides, mud and debris flows, rockfalls, etc. B. rivers, ocean shorelines, and alluvial fans C. beaches, windblown sand dunes, continental shelves, rivers, deltas, alluvial fans, debris flows or

underwater slumps

D. lake, deeper part of ocean, floodplain of river channel E. outer parts of deltas or floodplains, deep lake, deep ocean floor, etc. F. dry lake G. shallow ocean H. swamp or bog

18. Sample #4: What is the name of this rock?

A. breccia B. conglomerate C. sandstone D. siltstone E. claystone F. shale G. rock gypsum H. rock halite/rock salt I. micrite/limestone J. coquina K. fossiliferous limestone L. chalk M. oolitic limestone N. dolostone O. peat P. lignite Q. bituminous coal

19. Sample #5: Is this rock clastic or chemical?

A. clastic B. chemical

20. Sample #5: What mineral or material does this rock mostly contain?

A. gypsum

B. halite C. calcite D. dolomite E. plant material

21. Sample #5: What is a possible depositional environment for this rock?

A. area that experienced mass wasting such as rockslides, mud and debris flows, rockfalls, etc. B. rivers, ocean shorelines, and alluvial fans C. beaches, windblown sand dunes, continental shelves, rivers, deltas, alluvial fans, debris flows or

underwater slumps

D. lake, deeper part of ocean, floodplain of river channel E. outer parts of deltas or floodplains, deep lake, deep ocean floor, etc. F. dry lake G. shallow ocean H. swamp or bog

22. Sample #5: What is the name of this rock?

A. breccia B. conglomerate C. sandstone D. siltstone E. claystone F. shale G. rock gypsum H. rock halite/rock salt I. micrite/limestone J. coquina K. fossiliferous limestone L. chalk M. oolitic limestone N. dolostone O. peat P. lignite Q. bituminous coal

23. Sample #6: Is this rock clastic or chemical?

A. clastic B. chemical

24. Sample #6: What size are the grains?

A. boulders B. cobbles C. pebbles D. granules E. sand F. silt

G. clay

25. Sample #6: Describe the sorting of the grains.

A. very poorly sorted/poorly sorted B. well sorted/very well sorted

26. Sample #6: describe the shape of the grains.

A. angular/subangular B. subrounded/rounded

27. Sample #6: What is a possible depositional environment for this rock?

A. area that experienced mass wasting such as rockslides, mud and debris flows, rockfalls, etc. B. rivers, ocean shorelines, and alluvial fans C. beaches, windblown sand dunes, continental shelves, rivers, deltas, alluvial fans, debris flows or

underwater slumps

D. lake, deeper part of ocean, floodplain of river channel E. outer parts of deltas or floodplains, deep lake, deep ocean floor, etc. F. dry lake G. shallow ocean H. swamp or bog

28. Sample #6: What is the name of this rock?

A. breccia B. conglomerate C. sandstone D. siltstone E. claystone F. shale G. rock gypsum H. rock halite/rock salt I. micrite/limestone J. coquina K. fossiliferous limestone L. chalk M. oolitic limestone N. dolostone O. peat P. lignite Q. bituminous coal

29. Sample #7: Is this rock clastic or chemical?

A. clastic B. chemical

30. Sample #7: What mineral or material does this rock mostly contain?

A. gypsum

B. halite C. calcite D. dolomite E. plant material

31. Sample #7: What is a possible depositional environment for this rock?

A. area that experienced mass wasting such as rockslides, mud and debris flows, rockfalls, etc. B. rivers, ocean shorelines, and alluvial fans C. beaches, windblown sand dunes, continental shelves, rivers, deltas, alluvial fans, debris flows or

underwater slumps

D. lake, deeper part of ocean, floodplain of river channel E. outer parts of deltas or floodplains, deep lake, deep ocean floor, etc. F. dry lake G. shallow ocean H. swamp or bog

32. Sample #7: What is the name of this rock?

A. breccia B. conglomerate C. sandstone D. siltstone E. claystone F. shale G. rock gypsum H. rock halite/rock salt I. micrite/limestone J. coquina K. fossiliferous limestone L. chalk M. oolitic limestone N. dolostone O. peat P. lignite Q. bituminous coal

33. Sample #8: Is this rock clastic or chemical?

A. clastic B. chemical

34. Sample #8: What size are the grains?

A. boulders B. cobbles C. pebbles D. granules E. sand F. silt

G. clay

35. Sample #8: Describe the sorting of the grains.

A. very poorly sorted/poorly sorted B. well sorted/very well sorted

36. Sample #8: describe the shape of the grains.

A. angular/subangular B. subrounded/rounded

37. Sample #8: What is a possible depositional environment for this rock?

A. area that experienced mass wasting such as rockslides, mud and debris flows, rockfalls, etc. B. rivers, ocean shorelines, and alluvial fans C. beaches, windblown sand dunes, continental shelves, rivers, deltas, alluvial fans, debris flows or

underwater slumps

D. lake, deeper part of ocean, floodplain of river channel E. outer parts of deltas or floodplains, deep lake, deep ocean floor, etc. F. dry lake G. shallow ocean H. swamp or bog

38. Sample #8: What is the name of this rock?

A. breccia B. conglomerate C. sandstone D. siltstone E. claystone F. shale G. rock gypsum H. rock halite/rock salt I. micrite/limestone J. coquina K. fossiliferous limestone L. chalk M. oolitic limestone N. dolostone O. peat P. lignite Q. bituminous coal

39. Sample #9: Is this rock clastic or chemical?

A. clastic B. chemical

40. Sample #9: What size are the grains?

A. boulders

B. cobbles C. pebbles D. granules E. sand F. silt G. clay

41. Sample #9: Describe the sorting of the grains.

A. very poorly sorted/poorly sorted B. well sorted/very well sorted

42. Sample #9: describe the shape of the grains.

A. angular/subangular B. subrounded/rounded

43. Sample #9: What is a possible depositional environment for this rock?