Imagine,there you are, walking through the bush. You know the area you are walking through used to be volcanic, in fact there is a mountain close by which is an extinct volcano! You spy a funny rock while you're walking and pick it up. It's a odd shape, very round, but also a bit of a strange colour. Perhaps, if you're lucky it's a thunder egg!
When I took these thunder eggs to show the children, their reactions were wonderful - many and varied. They were all in agreement that not only are the insides of thunder eggs beautiful, the outside is really 'not much to look at' but that seemed to be where the agreement stopped! They had a long discussion about whether they were 'fairy houses' or the eggs which thunder was born from. You can probably guess, but the girls were all for the fairy houses, the boys preferred the thought of thunder being 'born' from these rocks.
The real story of how thunder eggs got their modern name is almost as fantastic as the stories the children made up. Thunder eggs are the official rock of Oregon (USA) and, according to the story, the pre-Columbian American's (or Native American's) thought the egg shaped rocks which they found when the soil weathered away were the eggs of the thunderbird which lived in the mountains. When the gods were angry at one another, they stole the thunderbirds eggs and used them as weapons, throwing them at each other. The gods the legends mention are probably the volcanoes which created the thunder eggs themselves. If you'd like to learn more about this legend click here or here.
So how do thunder eggs form? The scientists do not actually agree on how thunder eggs form, so there is no easy answer here. Some believe that thunder eggs were created by the expansion of hot volcanic gasses, others think they formed by a process of drying a volcanic colloid (gel). Certainly, volcanoes are involved in the process, and it is highly unlikely that they are spat out fully formed. Whatever the original process is, a cavity is left inside the rock which then fills with various different minerals, so thunder eggs can be all different colours and patterns! If you would like to learn more about thunder eggs, click here.
People love to display cut and polished Thunder eggs as they are so colourful and beautiful. Sometimes you see thin slices of them used to make jewelery such as pendants or large pieces displayed as mobiles. The children wondered why, despite their best efforts they could not fit what seemed to be the two pieces of the egg back together. Unfortunately a little is lost when the egg is cut open. Thunder eggs are very, very hard and require a special saw to cut them so if you are lucky enough to find one, no matter how hard you try you you won't be able to cut it in half with your Dad's saw! If you would like to learn more about preparing thunder eggs click here or contact your local lapidary club.