Introduction to Rocks - Rock Cards

Rocks come in a fascinating array of types, each with distinctive features and origins. Conglomerate, for example, is a coarse-grained sedimentary rock comprising rounded grains, while sandstone is another sedimentary variety known for its sand-sized particles and layered formation. Shale stands out with its ultra-fine grains that are often too small to discern without close inspection. In the realm of igneous rocks, basalt is notable for its richness in magnesium and iron. Coal, a historically significant sedimentary rock, is formed from plant matter that has transformed into carbon and is typically found in underground seams. Chalk, a soft and porous sedimentary rock, consists of calcium carbonate and is highly susceptible to chemical weathering.

Moving on to other sedimentary rocks, mudstone is characterized by its fine grains originally composed of clay and mud, while limestone shares a calcium carbonate composition with chalk. The metamorphic category includes marble, a transformed limestone that has been prized for sculpture for centuries, and slate, which originates from shale or silt. Schist is a metamorphic rock with noticeable bands of colour, and gneiss, common in regions like New England and the Rocky Mountains, is also metamorphic. Hornfels is an intriguing banded metamorphic rock created by the intense heat from igneous rock baking nearby shale or mudstone. Novaculite is a dense rock from the US and Japan, formed under extreme heat and pressure from marine animal remains and quartz crystals. Phyllite is predominantly made up of mica, while migmatite is a unique mix of metamorphic and igneous rock. Other igneous rocks include diorite, mainly composed of feldspar, gabbro with its coarse grains, and the well-known, hard granite. Hornblende forms deep underground, obsidian is a black volcanic glass that cools rapidly, pumice is a low-density rock with a bubbly texture from rapid cooling volcanic gases, tuff is made of volcanic ash, and rhyolite is a silica-rich volcanic rock.