This is a closed mining claim that contains some onyx. It is located in the Mount Baker–Snoqualmie National Forest so you will need to be prepared to travel on logging roads without cellular reception.
https://github.com/davepinch/pinchy.cc/blob/master/content/topics/places/mines/sweet-water-claim/sweet-water-claim.md
Acute triangle (Wikipedia) An acute triangle (or acute-angled triangle) is a triangle with three acute angles (less than 90°).
