A: That depends some on the settings, and how much protection your metal will give the stones, but in all probability, this wouldn’t last more than, say 5 years or so of use with reasonable care but constant wear, before the stones would look pretty trashed. And there are a lot of folks who’d treat it in a manner they thought reasonable, who’d find the stones trashed in less than a year.

Most of the “rainbow” designs that use tourmalines, if they need a purple, switch to amethyst for that color. While you’ll get dark blues, you’ll have a pretty hard time finding anything approaching a true purple in tourmaline. That’s the one color it doesn’t do well. Dark blues are usually tinged with green, not the reds that would be needed to get a purple, and the reds are tinged with orange/brown, not the purple hues. There just isn’t a color series between the blue and the red in tourmaline.

If you could overlook price, you can get quite a range of bold colors in diamonds, including the more economical radiation-treated ones for many of the colors. But their colors tend toward the pastel hues, and the red tones, (or more commonly, the pink tones, as true reds command unbelievable prices) will pretty much be restricted to the natural Australian stones, which are not cheap either.

Sapphires do come in all those colors. The reds, of course, are called ruby. Nice ones aren’t cheap, but you have several options, if price is a consideration. There are quite a number of types of synthetic sapphire, with the same physical properties as the natural variety, available in virtually all colors. If you include the similar material, spinel (which is slightly softer, but also slightly tougher) you can fill in more of the “cool” colors. Try to avoid, if you can, those spinels made as “triplets”, being top and bottom layers of clear spinel, with a colored cement in between. These look good, and are actually fairly durable, although they aren’t as good as the solid ones, especially in some of the harsher environments that they might encounter within the jeweler’s shop, like the pickle pot. But this type of synthetic is very durable, and very cheap. It is the stuff used in many class rings. More expensive versions of the synthetic material also are available, and look more like the natural stones. There are fewer color choices in those materials, though.

You might consider using mostly natural stones for the less expensive colors, and a good synthetic ruby for the red, as your budget allows. Any decent jeweler or gemologist can help you with these choices, and show you examples of the materials. There is one other material you might keep in mind. Synthetic cubic zirconia is made now in many interesting and vibrant colors. Although these are completely man-made with no natural analog, they nevertheless can be really attractive, especially in those colors that are not already so overused in commerce as to seem cheap and kitschy (We probably don’t need more “pink ice” on the market, do we?)

The key to this working well would be getting stones that are very nicely cut, and making the jewelry heavy enough to both protect these somewhat less durable (compared to diamond or sapphire) stones and allow for easy servicing of the jewelry at a later date, should it be needed to replace stones. They’d still be better than the tourmalines for durability, and the cost would likely be low enough that it would be practical, when ordering the stones, to get some extras to allow for easy maintenance, should you damage a stone in the future. (Of course, if you hate the idea of synthetics, as many people do, then forget I even mentioned this.)

Greater hardness usually also means greater durability, but the two properties are not completely identical. Jade, for example, is both much softer than diamond, yet is slightly harder to break in some directions. Diamond is very hard, yet somewhat brittle (though it’s still pretty darn tough, and in normal wear, holds up very well—much better than other stones, although it’s not indestructible. Sapphires and rubies, while very hard, can also be a bit brittle, while spinel and chrysoberyl, which are slightly softer, are harder to break and chip.

The thing to keep in mind here is the other side of the story. While some softer stones may be pretty resistant to chipping and breakage, it doesn’t do you much good if the stuff abrades and gets scratched up easily. A highly worn and scratched stone looks pretty junky, even if it’s not yet broken. Higher hardness helps reduce that wear and tear, even if it’s not always a guarantee against breakage. It’s also important to mention that cutting is important to durability as well. Stones with thin edges or shallow crown and/or pavilion angles will be more easily broken than those with thicker, less fragile edges. On the other hand, you shouldn’t overdo it either, as extra thickness adds little to the appearance of most stones, and can not only cost you more (for the extra weight) but make setting the stones more difficult, if the edge is too thick or the stone too deep for the design.