Natural Citrine or heat treated?
I don't know if you're aware of the fact that most citrine on the market is actually amethyst has been put into an oven and get heated to high temperature which results in a yellow-gold coloured amethyst, that resembles citrine.
Real citrine is made by Mother Nature for thousands of years under the surface.
There's nothing wrong with heat treated citrine if it's presented as heat treated but sometimes even traders don't know or not consider it ti be important. But for some people it might be.
Especially because real citrine is quite rare and therefore more expensive than heat treated amethyst.
How can you tell the difference?
Citrine is more like a clear quartz in their form and colour. It is usually pale yellow or a bit smokey like in the left picture above. If it looks like a golden amethyst point, it's definitely heat-treated (picture on the right).
In my personal opinion I don't mind heat treated crystals at all but people have a right to know what exatly they are buying as some of them would prefer real citrine if they knew at all!