My parents have found some unusual insect eggs in their garden in gravel and soil areas. Through leeching of rainwater and minerals from the garden soil, the eggs have been found gathered in certain areas. They are distinctly round and spongey, grey-blue in colour and the size and appearance of silver sugar cake decoration balls.
I've been told that if they had been white opaque in colour they are likely to be snail or slug eggs but as they're grey then no
I've kept some in jam jar as pictured in the photo. Any ideas if they are a common bug or possibly some new infestation? My parents have not come across them before.
Not an answer at this stage; just some thoughts...
Slug/snail eggs darken before hatching, but yours still do not look quite right for that.
I'm tempted to suggest they are seeds rather than eggs, but the sponginess does make eggs more likely.
Stag beetle eggs become grey and round, but they are only about 2mm diameter, which I think is smaller than yours (http://maria.fremlin.de/stagbeetles/lctable.html).
If they hatch before somebody identifies them, please post another photo here!