Obsidian is black and has a glassy texture. There are small little glass bubbles inside of the rock. You can find obsidian where lava flows are cooling.
Pumice is a light-colored, extremely porous igneous rock that forms during explosive volcanic eruptions.
Basalt appears black or grayish-black, sometimes with a greenish or reddish crust and it has a roughish texture.
Granite is a light colored igneous rock with grains large enough to see with the unaided eye. It is the best known igneous rock.
Diorite is a speckled, coarse-grained igneous rock consisting essentially of plagioclase, feldspar, and hornblende or other mafic minerals.
Slate is a fine grained gray, green , or bluish metamorphic rock and is flat. It also has different layers of rock.
Marble is a crystalline metamorphic form of limestone, tip
Hornfels is usually black or gray it is very fine grained. It is a fine-textured, Metamorphic rock formed by contact. Metamorphism.
Quartz is a white or none colored rock. It acquires in all mineral environments. Quartz forming only occurs in microscopic, compacted crystals.
Schist is coursed grained, it can be found in brown, black, gray and rarely red.
Shale is a soft, finely stratified sedimentary rock that formed from consolidated mud or clay and can be split easily into fragile slabs. Shale can be green, black, gray, brown and sometimes even peach.
Salt is a crystalline sedimentary rock. Salt occurs naturally in many parts of the world as the mineral halite and as mixed evaporites in salt lakes.
Coal is a combustible black or dark brown rock consisting mainly of carbonized plant matter, found mainly in underground deposits and widely used as fuel.
Amber is hard translucent fossilized resin produced by extinct coniferous trees of the Tertiary period, typically yellowish in color. It is often found in jewelry.
Chert is a hard, dark, opaque rock composed of silicon dioxide. Sheet is mainly gray, red or brown.