Congrats on your new little Crassula. These are quite forgiving, buy if the soil is too heavy and if your jar doesn't have a drainage hole it won't be good for the long run, because succulents need its soil to be rather dry to bone dry most of the time. The jar is very cute though.

I'm not sure what white dust you mean, is there a close-up picture for the white spots? The plant looks rather healthy for now, but yeah see how it does in a week or two.

Temperature wise I think you need worry not, but these do like quite a bit of sun and even thrives in direct sunlight. But yeah if you've decided to keep it as an office plant then hopefully it gets enough light through the windows.

Also since it's indoor you don't need to water these very often, I water mine every 10-14 days, and ESPECIALLY if you're growing it in the jar then you gotta be careful not to give it too much water.

Have fun and good luck!

Ok thanks DavidL i appreciate that its more ashy I guess

..i do love it in my jar but I will change it if I have too

That doesn't look bad, probably just marks from previous watering or fertilizing.

Yeah, see how it goes for you in the jar, just water very sparingly and don't water all the way through (to the bottom of the jar), of course you'll have to use your own judgement on that since you can't really "measure" how much water.

thank you