Final answer:
Slate is a foliated metamorphic rock formed from the metamorphism of shale, known for its ability to split into thin layers due to parallel arranged clay minerals and is very fine-grained, dense, and brittle. Option number 1 is correct.
Step-by-step explanation:
Characteristics of Slate
Slate is a foliated metamorphic rock that is known for its ability to split into thin layers or sheets. This feature, known as slatey cleavage, is a result of the parallel arrangement of its microscopic clay minerals. Slate is typically formed from the low-grade metamorphism of shale, and it does not have visible separate grains due to its very fine-grained nature. The rock is dense, tends to be brittle, and produces a clinking sound when struck. The original bedding of shale, which slate comes from, can sometimes be seen in outcrops of slate, where the foliation planes become visible.
Slate contrasts with non-foliated metamorphic rocks that do not exhibit a layered or banded structure. Unlike non-foliated rocks, which have mineral crystals growing in random directions, the minerals in slate are aligned, contributing to its ability to cleave along parallel planes.
When describing the texture of metamorphic rocks, including slate, terms such as 'foliated, nonlayered, very fine grained' are often used. This signifies that the rock has a foliated texture without pronounced color banding and that it has small crystal grains. It is worth noting that in comparison to igneous rocks, slate is relatively soft, and it commonly occurs in layers or beds.