The Art of Gem Cutting by Thomas Trozzo

picthomas-trozzoTom Trozzo provided the DCGIA members with insight into his process of cutting and faceting his award winning gemstones.  Although he still has German cobbling hammers with carbide tips, he no longer uses them for faceting.  Now a days he uses a Diamond Jem grinding unit, Diamond cutting wheels and diamond sanding belts.

Some of Tom’s equipment along with pictures are shown below:

A Diamond Jem by Raytech Grinding unit. 6 inch diamond wheels, working chrysoprase into a cabochon.
picgrindingChrysoprase, chrysophrase or chrysoprasus is a gemstone variety of chalcedony ( cryptocrystalline form of silica) which contains small quantities of nickel. Its color is normally apple-green, but can range to deep green.

picsawCitrine’s attractive color, durability and affordability as a variety of quartz, makes it a top selling yellow-to-orange colored gemstone. Citrine’s most popular shade is an earthy, deep, brownish or reddish orange.

Here Tom is blocking out and sawing citrine rough into a future award winning design pattern, we are sure.


Raytech-Shaw faceting machine with 6” cutting surface

picfacetronFacetron unit with an 8 inch cutting surface, the dop stick with gemstone rough is locked into Facetron jig.  The angle of the universal jig allows for positioning and shaping of the facets of the gemstone.  It is a manual process taking extreme patience and attention to detail by the gem cutter.

There was a variety of other special purpose pieces of equipment used by Tom as well, for accomplishing the finished product.

Tom also discussed gemstone treatments and how they affect a cutters ability to work with the treated gemstone materials.

Heat Treatment of gemstones, is usually stable, each gem material is different, so each heat process will also be different depending on the gemstone.

picheatHeat treatment is not an issue when cutting the untreated rough, as the heat treatment can then be applied after the initial faceting and after polishing.


Radiation Treatment is usually stable, again depending on the gem material, type of treatment and amount of time in the treatment process.  Radiation is usually done by gamma, linac (linear accelerator) or nuclear processes. Radiation treatment is not an issue during cutting but over time fading of some gem materials can occur.

Oils and Resin Filled Gemstones. Oil and resins filled gemstones can be problematic during and after cutting the gemstones.  Since the cutting blades and polishing wheels are impregnated with diamond powder, the powder can get into the fractures, causing darkening of the area where the oil or resin has been displaced.  The use of cleaning solvents will also pull oils and resins out of treated fractures causing the quality treatment to be lost.


picemerald2As shown with this Colombian Emerald, where the Oil treatment was removed from the gemstone, prior to re-faceting and the gemstone was re-treated with paraffin to improve the visual quality of the emerald.

Diffusion Treatments are typically a surface treatment, with only the first few millimeters of the gemstone taking in the color. This presents a great problem should the stone ever need to be recut or scratches removed.  Tom has heard of deep diffused treatments that penetrate color throughout the stone, but as of yet, has not worked on any gemstones so treated.  Dyed stones can of course be problematic when cutting, polishing and cleaning later on…

Working with designs in gemstones, the gem material, shape and balance of the rough, often determines the final design of the gemstone.

Tom also shared photos with the DCGIA members, of his many AGTA Cutting Edge Competition winning gemstones and his other industry award winners.

DCGIA Thanks Tom Trozzo for sharing a wealth of information and his award winning gemstones with our members and guests.

Summary Charles Marts

Photos provided by Thomas Trozzo

This entry was posted in Meeting Archives and tagged , , , . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s