Need please couple questions for my geology homework ! i would greatly appreciat

Question

Need please couple questions for my geology homework ! i would greatly appreciate it

Toilet Bowl, Oahu, Hawaii beach sandThis is an unusual green sand made almost entirely of crystals of the mineral olivine.

1)What does the presence of this mineral suggest how much these grains have been weathered and transported?

Sedimentary rocks contain a variety of clues that can help you figure out how and in what type of environment they were deposited. Use the descriptions below to help you determine in which environment the following rocks were deposited.

a)Sediment that was deposited on the bottom of a body of water is typically sorted by size (all the particles are about the same size) but sediment that was deposited as a mud flow is typically not sorted by size at all (all the particles sizes are jumbled together).

b)If detrital sediment is well sorted by size, the sizes of the sediment particles provide clues as to how fast the water was flowing. The larger the particle size, the faster the water must have been flowing.

c) As detrital sediment is transported by flowing water, the sedimentary particles bang against each other and wear each other smooth, rounding any sharp edges. Thus the more rounded the grains of detrital sediment the farther the sediment was transported.

2) Closely examine rocks #1 and #2. One was deposited on the bottom of a body of flowing water. The other was deposited as a mud flow. Which is which? Explain the reasoning behind your answer.

Rock 1.

Rock2

3) Closely examine rocks #3 and #4. Both rocks were deposited on the bottom of a body of flowing water. For which rock was the water flowing faster? Explain the reasoning behind your answer.

Explanation / Answer

1. The hawaii beach sand is unusually green and is composed mainly of mineral olivine. Olivine is olive- green in colour which imparts green colour to the beach sand of Hawaii. This is a common mineral found in mafic rocks and ultramafic rocks like gabbro, basalt, dunite, peridotite, diabase. Since the crystallization temperature of olivine is very high, it is the first minerals to be crystallized from a magma. It is also the first mineral to be altered by weathering because its temperature and pressure conditions are very different from that of near surface conditions. This is the reason that olivine is not a common mineral in the sedimentary rock. Although it can be an an abundant mineral in the sands or sediments when the deposit formed very close to the source. The green beach sands of Hawaii is made up of basaltic lava which has a high content of olivine. The green beach sands of Hawaii is derived from the nearby littoral cone. These cones are eroded by the oceans which crushed the rock into fine sands which is then transported to the Hawaiian beach.

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