This object is 14 cm along the longer length 10cm across, radius approx. 7cm. It weighs 1.9KG. It is shaped like half a rugby ball, smoothish but with tiny pitting all over. Smnoothest part is inside the cavity (top picture). Unfortunately there is no record of where it comes from. It belongs to a friend of mine who has used it as a doortsop for about 50 years and is now curious to know more about it.
Yes - curious object.
Rather than transcribe questions into this posting, may I refer you to these pages to work through; they help determine if an object is a meteorite but may alternatively point in other directions:
- http://epswww.unm.edu/iom/ident/index.html (also a useful table of densities)
Thank you very much for these links. The first once appears to be 'down' for maintenance but the Australian and Natural History Museum ones have been very useful. My friend's object is not magnetic so that seems to rule it out as a meteorite; also its density is approx. 2.99 g/cm cubed, a bit on the light side for a meteorite. I wondered if it could be a volcanic bomb but although its size is commensurate with that it doesn't look like any examples I can find pictures of on the internet. The other option seems to be that it is industrial slag as it has a molten, glassy sort of appearance in parts, and is not metallic.
Any further observations will be gratefully received,
The first link is up again now. But you've covered most of the key points from the other two sites.
It could be a volcanic bomb; it looks somewhat like part of a more rounded object that split in half while still hot and soft, perhaps aided by expanding gas in the central cavity. Guesswork, but possible scenario.
Slag is also possible. However, in both cases it would be quite likely to find vesicles (holes formed as gas bubbles).
So, as with many such objects, the easier tests take us only so far...
We'd need to make a thin section and look at it under a petrological microscope - to identify its make-up in terms of minerals (or discover it is amorphous or cryptocrystalline, perhaps). That's probably beyond your practical options, unless you know somebody studying geology at uni.