The most common types of cave decorations, or more correctly, 'speleothems' seen in Western Australian caves are straws, stalactites, stalagmites, columns, shawls, helictites and flowstone.
Cave decorations are made from calcite, a crystalline form of calcium carbonate.
Straws are long, thin stalactites with a hollow centre resembling a drinking straw in appearance. Numerous straws hang from the roof of Lake Cave. One of the world's longest straws can be seen in Jewel Cave, it measures 5.43 metres in length.
Stalactites also hang from the roof of the cave. Often the centre of the straw has been blocked forcing the solution to run down the outer surface. In this way the straw is thickened as well as lengthened. Lake Cave has some excellent stalactites.
Stalagmites grow up from the floor and are formed by drops of water falling from the roof. There are some huge stalagmites to be seen in Mammoth Cave.
Columns form when a stalactite and stalagmite join. Mammoth, Lake and Jewel Caves all have massive columns.
Shawls are wavy sheets of calcite that hang from the ceilings and walls. Mammoth Cave has a beautiful orange shawl, coloured by tannins from the leaves on the forest floor above.
Helictites defy gravity growing in many different directions, twisted and worm-like. They grow via a small capillary canal in its center, which is often under pressure, with surface tension and attraction they grow in any direction. Jewel Cave has thousands of these bizarre decorations.
Flowstone solution seeping out of the wall of the cave or flowing over a gently sloping section of floor can deposit sheets of calcite over a relatively large area. Jewel Cave has a beautiful area of flowstone called the Frozen Waterfall.