You have yellowish smokey quartz similar to cairngorm crystals of the Cairngorm Mountains of Scotland. Non-Scottish examples are marketed under the trade name “bumblebee.” The smoky color results from free silicon formed from the silicon dioxide by natural irradiation
Often times, smoky quartz can be turned into a citrine-like yellow through heat-treatment. With that being said, such heat treatments result in a significantly more vibrant product.
I would assess, with the above information, that these are likely natural.