What is meant by "bands" in this sentence?

Question

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A log of the core should be made noting especially the major coal lithotypes, presence and thickness of rock *bands*, slickensided surfaces and major joints in the recovered length of coal.

Answer 1

In this case, "bands" means something like layers.

As you go down in the earth, the type of rock you see changes.

Answer 2

Like the bands in a tree tell it's age & type of year it was.Rainy year,drout.fire etc.

Answer 3

"A strip or stripe that contrasts with something else in color, texture, or material." -- from Dictionary.com