Screens stones which are identified as natural and not high temperature high pressure treated having the chemical vapor deposition method applied.From HRD Antwerp, the D-Screen is a compact and practical test that quickly rules out whether a diamond has received HPHT treatment or is synthetic (lab-grown). The D-Screen signals if a diamond should undergo closer examination by a grading lab. Can be used with diamonds from color D to J and from .20ct to 10 carats. With a quick response time, diamonds test almost as fast as you can place them into the unit. Green indicator means the diamond is not synthetic and not HPHT color enhanced. Orange indicator means the stone requires further examination by a grading lab. Unit is barely larger than a stapler, the D-Screen operates on 110-230 volts with supplied adapter or on a 9-volt battery (included). One-year warranty.