This is a close up picture that shows another the rock that is in the active min
ID: 801786 • Letter: T
Question
This is a close up picture that shows another the rock that is in the active mining site and is one of the ore rocks. The groundmass is crystalline and the crystals are so small they cannot be seen without magnification The larger pieces seen are not individual mineral crystals but other pieces of rock that are now incorporated into this rock. .
Rock piece A: Looks similar to Rock Sample #1. Crystalline, dominated by light colored, visible crystals that are randomly oriented.
Rock piece B: Alternating dark and light colored bands of visible minerals. The crystals are large enough to be seen. Looks similar to Rock Sample 2 in this homework.
1.
What is the rock type of this sample?
sedimentary rock
igneous rock
metamorphic rock
2.The crystalline texture of this rock is called
3.Based on the texture of the rock, what can you determine was the rate that the mineral crystals formed in the ground mass (aka the crystallization rate; Slow crystallization, fast crystallization, two rates of crystallization, first slow then fast)? Explain your reasoning in 1-2 sentences.
a)sedimentary rock
b)igneous rock
c)metamorphic rock
Explanation / Answer
By seeing and anaylizing the mixed rock samples, fine grained crystal of light colours may be of volcanic rock with higher silica content. on the other hand the large rock pieces have been suspended/embedded into ground mass or matrix of fine grainis. This may be the case of porphyritic texture (mixed up of fine and coarse grains).
1. Possibly it is an igeneous rock sample with fine grains, but band of dark and light color of rock sample could be related with sedimentary rock or a transition of sedi to igneous rock.
2. Porphiritic texture
3. fine grain crystals form due to rapid/ fast rate of crystalization of the ground mass.
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