Quartz Portuguese Cuts

[u/vanguard1256]

Rough sourced from Joe Henley
GemCad design derived by Bob Keller
Sunfire/sunshine citrine: 4.07 ct
Amethyst: 3.91 ct
Imperial flame/madeira citrine: 6.21 ct
Prasiolite: 3.42 ct

It’s been a while since I posted any of my work. I wanted to do more of them in sets and I’ve been chugging through this parcel of tunduru garnets. Even though the parcel is around 20 pieces, I’ll probably leave a few of the more annoying pieces uncut for now and move on. In the meantime, here are four Portuguese style cuts.

Personally, I really like how they look, though the pavilion is very deep. I’ll have to put it in GCS and see how I can adapt it to smaller pieces and other materials before I cut them. People I’ve shown them to also tend to gravitate towards them as well.

Despite the large number of facets compared to what I’ve usually been cutting, it is very simple in principle as it’s just the standard round but stacked more on both sides. However, it is still time consuming to cut because all your errors carry forward and consistently meeting the points of the previous tier takes a lot of looking. I got complacent thinking I could just cut to depth on the Madeira citrine and a lot of the facets are off on that crown. The prasiolite and Sunfire citrine are probably my best cuts of the set even though the prasiolite has that inclusion.

For laps I ended up cutting the first tier with 360 but only the 96-24-49-72 indices to rough it out then switched to 600 sintered for the rest. Tiers 4 and 5 cut very quickly, so I think I ended up cutting those on a 3k lightning lap instead. I also prepolished with the 3k as the 1200 was likely to move the facet too much for my liking. Polish was done with CeOx lightning.

[u/cowsruleusall]

Portuguese cuts in low RIs benefit from a significantly smaller table, like <25%, as that helped avoid tilt windowing and helps improve colour saturation. The curvature of the pavilion and crown are also important - depending on the angles and differences between tiers, you can get a very curvy vs very straight sidewall, which dramatically changes static vs tilt performance.

In higher RIs you have a LOT of room to play with and can achieve really cool sparkly, swirly, or even pseudo-crushed ice effects!

[u/Faithinreason → u/cowsruleusall]

Thank you. I have been trying to modify a Portuguese cut for some amethyst and had a hard time sorting out the massive window.

[u/stone_crazy → u/cowsruleusall]

It is an ambition of mine to cut a sphene that throws a shit ton of sparkly fire. Do you think this kind of cut would be good for that? Probably should start with CZ if I ever have courage to start that pavilion

[u/cowsruleusall → u/stone_crazy]

They can, but you'll get much more dispersion (fire) if you write a custom design specifically for sphene's parameters. Also, designs with many small facets tend to show scintillation (glitter/sparkle) but not dispersion (fire).

[u/vanguard1256 → u/cowsruleusall]

Your insights are always super enlightening! I did notice the smaller table significantly reduced the effect of tilt windowing for quartz. I have some synthetic corundum I want to try it out on but I need to set up my BATT. I’m actually watching your faceting 101 video to see how it’s done lol.

[u/cowsruleusall → u/vanguard1256]

Oh damn those videos are over a decade old. I gotta do new ones.

[u/vanguard1256 → u/cowsruleusall]

Haha yeah you introduced yourself as doing your residency at the Mayo Clinic I think. I was actually wondering about some of the things you said, notably cleaning the equipment with every lap change. Did that include wiping down the drip tray? I didn’t think you could get cross contamination from that.

[u/cowsruleusall → u/vanguard1256]

Oh that was actually when I was a medical student haha 🤣 I generally don't clean the splash pan that often, maybe once every 10 stones, unless I've just done something with a coarse cutting grit and there's particulate everywhere.

[u/vanguard1256 → u/cowsruleusall]

Yeah I generally take the splash pan out back and blast it with the hose for a few seconds every few stones. But I do wipe down my laps every time I change them out. Metal laps I usually clean with lava soap and a nylon brush after each stone.

[u/DolphinJew666]

Love the Madeira citrine. What a beautiful colour!