Finding ions in water samples
It's Silver(I) Hydroxide

The solution was very alkaline, as evident by it's pH value of 14. Although  $\ce{AgOH}$ is sparingly soluble, with a $K_{\text{sp}}$ of $\pu{6.8×10^{-9}}$, under alkaline conditions it precipitates as a brown solid. 

This is a picture of precipitating silver hydroxide. Is it what you saw as well?