#tsilasite

Firstly, Yellow Tourmaline boosts personal power, spiritual growth, and considered an energizing and action stone.  An ability you can take from this is advanced shape shifting (something on par with Amethyst’s) where they can maintain a shape shifted form for much longer than other gems. Another could be energy related: they can increase the power of themselves or others via energy, steal and absorb energy, use raw energy to attack, etc. On par with that, Yellow Tourmaline is an illumination and enlightenment stone. We could take that in a literal sense and give them pyrokinesis or solar abilities. This color also deals with truth and honesty so perhaps your gemsona could be able to tell when others are telling the truth. Finally, all tourmalines and pyro- and piezo-electricitc. Electricity could be considered too.