* Lava is made of minerals. Volcanic rock, or igneous rock, is formed from cooled magma or lava. These are essentially mixtures of various minerals, like feldspar, quartz, mica, olivine, and others.
* Layers in igneous rock indicate different cooling phases. Igneous rocks often have layers due to variations in the composition of the magma or lava, the speed of cooling, or even the presence of gas bubbles.
* Lack of minerals is impossible for igneous rocks. Even if the rock is very fine-grained, it would still be composed of microscopic minerals.
Therefore, a rock with visible layers and no minerals would be more likely to be a sedimentary rock. Sedimentary rocks are formed from the accumulation of sediments like sand, silt, clay, and organic matter. These layers are often visible, and the rock may lack visible individual minerals if the sediments are very fine-grained.
Let me know if you have any other questions about rocks!
