Rocks used in the Rocks and Fossils Lesson

In the Rocks and Fossils workshop, children learn about and handle 3 kinds of igneous rocks and 5 kinds of sedimentary rocks. In small teams (of 3 or 4) children handle the rocks, examine them with a hand lens, and try to identify them, based on prior teaching and a descriptive guide.

Rock types: limestone, shale, sandstone, coal, flint, granite, basalt, obsidian.

Note: the 2013-14 brochure states that children will see 10 rocks. After delivering the lesson a few times I decided this was too many for young children to take in and remember, so I have reduced it to 8. I have taken out mudstone and chalk, because the former is a variant on shale and the latter is very similar to limestone.

The rocks are shown here, with a brief description of each below.

 Sandstone rocks near West Kirby on the Wirral, showing bedding

Top row, from the left:

Mudstone - sedimentary, fine grained, dark, similar to shale but with less obvious layers (not included in the lesson)

Limestone - sedimentary, fine grained, powdery feel, fairly easily broken, white to grey, made from tiny particles of calcium carbonate shells or precipitated from water, fossils common (e.g. Carboniferous coral reefs in the Peak District and North Wales)

Coal - sedimentary, black, with some shiny and some matt layers, made from compressed plant material, fossils may be visible, mainly formed in the Carboniferous which is named after it (Carboniferous means 'coal bearing'), many sites in the north and midlands mined for fuel

Shale - sedimentary, fine grained, grey to black, made of many thin layers which usually break apart easily, fossils common

 


 Bottom row, from the left:

Obsidian - igneous, volcanic glass, formed when magma cools very rapidly (e.g. due to water), smooth and shiny, usually black, may be brown due to presence of iron oxide

Granite - igneous, hard, formed when magma solidifies slowly underground, made up of three main minerals - feldspar, mica, and quartz, has visible crystals of various colours

Basalt - igneous, grey to black, formed when magma solidifies above ground (on land or ocean) - the ocean floor is almost entrely made of basalt, very fine grained, heavy, and hard

Sandstone - sedimentary, made of sand, mainly small particles of quartz, cemented together by other substances, can be very soft or fairly hard, grain size varies but grains are visible, formed either by water sedimentation (rivers, seas, grains have sharp edges) or by wind (dunes, grains have rounded edges), colour varies according to amount of iron oxide coating the grains, may contain fossils but less often than shale or limestone

Flint - sedimentary, nodules form from quartz in other rocks, especially chalk, hard and glassy, used in the stone age to make knives, axes, and arrow heads, usually grey to black or yellowish, often white on the outside, can contain fossils

Chalk beach near Bridlington, Yorkshire
Birley Quarry, cut from limestone