This agate formed in association with a yellow jasper (which is predominantly comprised of silica).

Before I cut this Carver find, it displayed a curious metallic sheen which was in fact what initially drew my attention to it.  The sheen was very different from the sheen observed from other quartz and jasper materials.  This metallic sheen appears quite clearly on the bottom of the pictured cabochon.

The rounded surface of the cabochon shows agatization and two visible “vugs.”  The stone from which this cab was cut also had a curious and unexpected heft (weight) that, combined with the metallic sheen, suggested a metallic component had mixed with jasper and formed  a metallic mystery agate that had not been previously observed on The Carver agate field.

If I can find out what metal is involved I will update you.