Note:  This item features a cluster of mostly blue quartz crystals from Crystal Hills, Arizona, USA.  The site, approx. 30 miles South of Quartzsite, was closed to digging some years ago.  I have no idea what the inclusion is that causes the effect but it certainly makes both an interesting and pretty display specimen.  You can see a small DT that lays on the surface slightly below the center in the photograph  The photo doesn't do the cluster justice - it is much nicer in person.