Tourmaline

I went digging through my little dragon hoard today, looking for inspiration, and was reminded how much I like tourmalines.

Sapphire may come in as many colors, but for gems as bright, clear, and large as what you find in tourmaline a person will end up paying a hefty premium. Especially if the sapphire falls into the red color range where it can be marketed as a ruby.

Red tourmaline – deep pink to ruby

And when it comes to greens, give me a tourmaline over an emerald any day. Emerald is about the same as tourmaline on the Mohs hardness scale – 7.5 – but tourmaline is tougher and less prone to fracturing or chipping. Take it from someone who has set a lot of both of them over the years.

Green tourmaline – mint to deep forest

If you are interested in the nitty-gritty stuff like chemical composition (boron silicate compounded with trace elements) then the Wiki page on tourmalines is the place to go. There you can take a deep dive into the 33 different recognized minerals in the tourmaline group and what gives them each their distinct colorations.

Small example of different shades and shapes

Tourmaline is not a rare mineral, although some of the nicer red pieces are harder to come by than they used to be, and prices on those have increased accordingly. Brazil produces the most volume at the moment, but gem quality pieces have come from almost every corner of the world. Even places like the states of Maine and California in the US have produced some extraordinary specimens.

Black tourmaline, also known as “schorl”, can be found just laying on the ground in the southwest desert of the US.

Black tourmaline crystals found outside San Diego CA

One of the best known characteristics of some tourmaline crystals is their bi-color nature. The most common is the pink and green combination known as “watermelon” tourmaline.

Pink and green tourmaline crystals

Tourmaline is also one of the minerals that can exhibit chatoyance – the “cat’s eye” effect. This is caused by thousands of tiny parallel tubes forming in the crystal. When those specimens are properly cut the incoming light gets reflected back in a line that tracks across the surface of the cabochon.

Green cat’s eye tourmaline cabochons

If you find yourself inspired to add a bit of really nice color feel free to drop us a note on the contact page. Or put a picture of your own favorite piece of tourmaline in the comments below.

Can a mokume ring be sized?

Solstice ring on sizing mandrel

Yes! Certain styles of mokume ring can be sized, within limits. But not all jewelers are able to size a mokume ring. As a general rule, the only person really qualified to size a mokume ring is the one who made it in the first place. Sizing mokume is not like sizing any other kind of precious metal ring. No matter the skill level of the jeweler, if they have not had years of experience with the mokume there can be problems.

Mokume starts as a stack of precious metal sheets containing different colored alloys, usually between 2 to 5 colors. Each of these metal alloys has a different set of characteristics – melting point, rate of work hardening, amount the metal can be worked before tearing, temperature at which is can be annealed to soften the metal again. When you fuse these metals together using diffusion bonding other strange things begin to happen. Without getting into the metallurgy, the bonded layer between the metals can have a lower melting point than the surrounding parent metals.

When a soldering alloy is also introduced into a cut seam, which happens all the time in normal ring sizing, there can be a cascade effect along the diffusion bond at low soldering temperatures. When this happens the colors in the ring melt together into a muddy new alloy that we lovingly refer to as mokumelt. The ring is basically ruined at this point.

Let me be clear – when soldering rings, even the low temperatures are still very high, over 1000 degrees in most cases. Your mokume ring is perfectly safe at any temperature you will expose it to.

Another common sizing method on standard rings is to use a ring stretcher. But the metals in mokume each expand at a different rate, which causes stress between the layers and can tear or shatter the ring if it is taken too far without proper annealing in between stretching.

Here again, the stresses involved with stretching rings are hundreds of pounds per square inch. If you ever subject your ring to that kind of force I’m much more worried about your hand than the ring.

So the first choice is to always take the ring back to the store where it was purchased. If that is not possible please feel free to drop us an email and we will figure out the best way to make your ring a comfortable fit again.

Our mokume rings can be sized, in general, up or down 1.5 sizes. There are exceptions to this – stone setting being one of those. And there may be options to take certain rings farther up or down if needed.

As always, if you have any questions or concerns please drop us an email.