Would anyone know what this is?

[PS1876]

Found this odd pebble on the beach in Sydney, Australia.

Not sure if it is some sort of waste slag or natural. not magnetic.

Any ideas much appreciated.

Thanks!

 

[Tony in SC]

Looks like a piece of very weathered coral, or a fire nugget?

 

[PS1876]

Thank you for your reply Tony. It seems to be too hard for coral, I can't scratch the brown material with a knife but was able to make a very small scratch with a corner of a piece of tourmaline. The porous structure and black inclusions look like it formed in high temperature.

 

[ToddsPoint]

Looks like granite. I see quartz, mica, and feldspar. Gary

 

[bowwinkles]

I seen something very much like that and I was lucky, it did not make a stain on the carpet.