https://github.com/davepinch/pinchy.cc/blob/master/content/topics/mathematics/shapes/pentagon/pentagon.md
Rockhounding Washington Green Opal From a Diatomaceous Earth Mine (YouTube) This location is a fun little stop off I-90 north of Vantage, WA. This is an active mining operation so going during business hours may be an issue so it’s best to stick to the weekends, and after 5pm.
Pentagon (Wikipedia) In geometry, a pentagon (from Greek πέντε (pente) ‘five’ and γωνία (gonia) ‘angle’) is any five-sided polygon or 5-gon. The sum of the internal angles in a simple pentagon is 540°.
