By Duncan Miller

(This is a follow-up to a previous article on faceting quartz, to be found with other faceting articles on the club’s website 

Every faceter knows quartz, those great big glassy-looking chunks that seem to cry out to be turned into doorknobs. Or pretty, golden ‘citrine’ that can cut brilliant yellow stones. Or glowing, dark purple amethyst with seductive blue flashes, dreamy rose quartz, or rutilated quartz with geometric golden blades. The range of possibilities is vast. The material is relatively inexpensive. What’s not to like? 

Quartz is not the easiest material to facet and often it is disheartening for the beginner battling to get a good polish. But let’s start at the beginning. If you are going to cut a lot of quartz you need a coarse lap to remove surplus material, or you need to grind preforms on a vertical wheel. A 320 mesh electro-bonded topper works well and when it wears out you just throw it away and buy another. Or you can charge a copper lap with coarse diamond yourself, and replenish the charge as necessary. Quartz swarf tends to clog diamond laps, so clean them thoroughly after use. I collect chunks of pumice off the local beach and grind that with lots of running water. It cleans electro-bonded and sintered bronze laps quickly and efficiently. Alternatively, scrub the lap under running water before the swarf has had time to dry out and set hard. 

Selecting material usually is easy. Unless it has attractive inclusions, and they cover a wide spectrum of the mineral world, avoid material with cracks and veils. Although, if you are lucky, internal flaws can produce rainbow interference colours that enhance an otherwise plain stone. Different colours of rough present their own selection issues. Amethyst can be too dark, resulting in an almost black stone. But many of these respond to cautious heat treatment in a closed kiln. Quartz from various different localities responds differently to treatment, either by heat and/or radiation, to produce a wide variety of colours not encountered naturally (see long discussion here:,55,350011,350166#msg-350166). 

The problems in cutting facets are few. The only difficulty I have experienced has been with some rutilated quartz, in which a few of the straight needles actually slid back and forth from one side of the stone to the other, protruding further and further as you cut opposing facets. The solution was a drop of cyanoacrylate (super glue) at either end to hold the needles in place during fine grinding. 

Polishing can be a different matter though, and many people struggle to get a good polish on quartz. As with all stones, a fine pre-polish – 3000 or 8000 mesh – is a pre-requisite. Cerium oxide and zirconium oxide are the oxides of choice for polishing quartz, using a very thin, water-based slurry. Polishing laps impregnated with these oxides are available. I have graduated from using a Lucite lap with cerium oxide to a Gearloose Creamway lap with zirconium oxide; and completely failed to be able to polish quartz with a Gearloose Darkside lap. Other people have no trouble with the Darkside. Some polish quartz with 60 000 mesh or 100 000 mesh diamond on soft metal laps like tin/lead or Batt, or on specially formulated polymer composite laps like Gearloose’s Diamatrix. You use whatever works for you.

One of the vexing issues in polishing quartz is caused by Brazil twinning and is particularly evident in amethyst polished with oxides. This takes the form of geometric pattterns of relief that appear on some facets, due to differential hardness in the twin lamellae. It is best avoided by ensuring that you have a very fine pre-polish and don’t need to polish for long, or to resort to diamond polishing.

 Photo: Geometric polishing relief caused by twinning in quartz, viewed with oblique lighting.

Below is a selection of different quartzes cut in various designs by Jo Wicht. Virtually no piece of rough used here cost more than R100, so quartz for her has proved a fun and inexpensive way of learning to cut gemstones as a hobby. Most of these stones were pre-polished at 3000#, and polished on a cerium oxide Ultralap. 

Varieties include: rock crystal, smoky quartz, rose quartz, green quartz (prasiolite), yellow quartz (citrine), purple quartz (amethyst), smoky quartz with rutile (largest sphere), blue chalcedony, blue lace agate, motorolite, chrysoprase, banded agate, and carnelian.

Photo and Cut Stones by Jo

105 ct Topaz in an Emerald Cut by Sigward Killat

This took a year to complete, partly because Sigward had to devise his own methods

 for polishing the very large table.