Cutting Cubic Zirconia

(via Gem Cutter, March 1982) Wahroongai News writes:

We have been asked to furnish information about cutting cubic zirconia. As is usual in the faceting field, various cutters develop their own techniques but a little research brought the following results:

The recommended proportions appear to be 1/3 crown and 2/3 pavilion with the table 55% of the width. For cutting round brilliants, one cutter suggest crown mains 35º and pavilion 41º whilst another quotes 34½º and 40¾º respectively. The critical angle is specified as 28º. Yet another experienced cutter stated that the Barion cut, originally developed for diamond cutting, is quite ‘spectacular’ in cubic zirconia.

‘Make haste slowly’ is the opinion of some facetors; it is necessary to proceed by degrees. First use 600 micron diamond on a copper lap with water; followed by 1200 micron on copper with oil; then 3000 micron on copper with oil. Don’t overdo the diamond—a little goes a long way with cubic zirconia.

A smooth lap is needed—a well worn one seems to work best. And—avoid contamination at all costs! Another opinion was that one needed to use only a medium diamond disc (260 grit) and then proceed to polish. All agreed that a fine satin finish at this stage meant less polishing and that the polishing should be done with Linde A on a tin lap, well scored, and at a moderately slow speed. The only alternatives suggested were ¼ micron diamond dust on a zinc or a ceramic lap.

Incidentally, it is interesting to note that cubic zirconia was originally produced for scientific and technological purposes and its use in the gem and jewelry trade was merely a side issue. Also, the colors in which is now produced are derived by purposely adding, usually a minute quantities, some impurity (called ‘dopant’) and that many of these additives are rare-earths.

Dopant used: Cerium; Color produced: Yellow-orange-red
Dopant used: Chromium; Color produced: Olive
Dopant used: Cobalt; Color produced: Lilac
Dopant used: Copper; Color produced: Yellow
Dopant used: Erbium; Color produced: Pink
Dopant used: Europium; Color produced: Pink
Dopant used: Holmium; Color produced: Pink
Dopant used: Iron; Color produced: Yellow
Dopant used: Manganese; Color produced: Brown-violet
Dopant used: Neodymium; Color produced: Lilac
Dopant used: Nickel; Color produced: Yellow-brown
Dopant used: Praseodymium; Color produced: Amber
Dopant used: Thulium; Color produced: Green
Dopant used: Titanium; Color produced: Yellow-brown
Dopant used: Vanadium; Color produced: Green