Final answer:
To classify the rock samples, examine the quartz grains' shape and arrangement, texture, and signs of foliation to distinguish between igneous, metamorphic, or sedimentary rock. Igneous rocks show interlocked grains, sedimentary rocks include cemented grains or precipitates, and metamorphic rocks feature foliated mineral structures.
Step-by-step explanation:
The question asks for the classification of rock samples into igneous, metamorphic, or sedimentary based on the observation of quartz grains in photomicrographs. To categorize the samples:
- Igneous rocks form from cooled magma or lava and typically display interlocking mineral grains of random orientations.
- Sedimentary rocks are comprised of weathered rock fragments that are cemented together or minerals precipitated from a solution and show clastic or chemical textures.
- Metamorphic rocks are altered by heat and pressure from pre-existing rocks and usually have foliated structures due to the reorientation of minerals.
When classifying the samples, consider the following attributes:
- The shape and arrangement of the quartz grains.
- Texture indicating a cooled magma/lava (igneous), cemented grains or precipitated minerals (sedimentary), or reoriented minerals due to heat/pressure (metamorphic).
- Any signs of foliation or lack thereof which would point to a metamorphic rock.