Could be I suppose; I don't know much about the sorts of common issues one sees on Macs. But I've never seen anyone with this before. It's only certain objects, so I want to say a cache rebuild might sort it - have you tried this yet? Or, have you tried fiddling in your graphics settings, and seeing whether a certain configuration/effect is causing this?
As additional information, is it always the same items that are black? And what are your machine specs, including graphics.
Hm, well, to be fair, the game has moved on but your machine has not. Those are the sorts of specs I was running just over a decade ago. But I'm not convinced that should mean some items are black and some aren't. By the way, you never answered the question regarding whether it's the same items each time - if it is, that might suggest a property of those items; some texture or effect on them, which would potentially indicate your graphics hardware isn't capable of rendering them properly (which may be fixed by fiddling with graphical settings - which you also didn't comment on).
To clear your game cache, follow the instructions here: https://support.runescape.com/hc/en-gb/articles/360001441169-How-to-clear-your-cache-
One thing that article doesn't mention though is that you'll need to let the cache rebuild afterwards. Once you've cleared the cache, log into the lobby - and sit there. Don't log in.
Bring up the developer console by holding the alt key and pressing tilde, then type "displayfps" in the console, and hit enter. In the top-right, you'll see detail regarding "Disk Cache" - wait for it to reach about 6-8GB, turn a purple colour and stop increasing in size, and you'll know the cache is downloaded again.
You can hide the debug info by runnin the "displayfps" command in the console again, and the console can be hidden the same way it was opened.
- Last edited on 15-Jul-2019 12:22:59 by Moneybucks