I think I need some tips onto how to tell them apart.  On ebay there are some items marked as "cast iron" and "used", but are silvery grey.  I've even emailed the seller who assures me they are cast iron because they are heavy.  But they are silver, not black.  So maybe they haven't been used like she says in her description.. I just don't know.

BUT I was walking through Woolworths yesterday and I lifted up a cast aluminum baking dish and it was very heavy (and black) like cast iron. 

But also on the weekend I attended a fleamarket where I saw a cast aluminum gem tray and a cast iron gem tray at different stalls.  This cast aluminum gem tray was incredibly light, nothing like the cast aluminum oven tray I saw at Woolworths.

I bought the cast iron one (see photo compared to round gem tray I bought last week that has been used) and you can see the colour comparison (cast iron gem tray is silver, so I am assuming it hasn't been used. Incidentally it is marked Simpson (like the home appliances) and is of terrible quality cast iron.  Really shocked by how grainy it is.  I know they made cast iron stoves back in the olden days, so I hope they weren't the same poor quality of cast iron LOL!!

So I guess I just want some extra reassurance in how to buy cast iron via ebay.  Is "heavy" enough as a decription if the item isn't black.  Is there anything else I should be looking for?

Thanks

Good Mick, the magnet test is the best for a novice. Like I said in an earlier post you've gotta be wary, I've seen stuff on eBay claiming to be cast iron when a man on a galloping horse could see it was aluminium.

VM's gem scone tray marked "Simpson" is the real deal, gee, they musta made millions of them !

pd

I've got a nice little 3m measuring tape about  1.5" x 1.5" which I carry in my purse.  This has a magnet on it.