Color and form are my artistic favorites, so it makes sense that I would be drawn to the realm of gemstones, which span the color wheel and offer endless opportunities for different combinations.

This is a classic watercolor inspired color wheel, whose primary colors are cadmium pale yellow, phthalo blue and alizarin crimson. These are used to create secondary and tertiary colors. The links below group jewelry items by the dominant color in the piece; for some items, this is subjective due to my love of color variety!

Color groups:

• Yellow (citrine, lemon quartz)
• Yellow-green (peridot)
• Green (emerald, malachite, tourmaline)
• Blue-green (turquoise, apatite, aquamarine)
• Blue (sapphire, kyanite, lapis lazuli)
• Blue-purple (iolite, tanzanite, dumortierite)
• Purple (amethyst)
• Red-purple (garnet, tourmaline)
• Red (ruby, rhodochrosite, pink topaz)
• Orange-red (carnelian)
• Orange (moonstone, sunstone)
• Yellow-orange (amber, citrine)
• Neutral-light (moonstone, crystal quartz, limestone)
• Neutral-dark (labradorite, onyx, jet, jasper, obsidian)

Interesting facts concerning color in gemstones: sometimes the color difference arises from a small change in chemical composition. For example: amethyst and citrine are the same chemical structure (quartz - SiO2) with differences in trace amounts of iron. Amethyst and citrine can form in the same crystal, a gemstone called "ametrine" with a striking complementary color contrast.

Many gemstones are heated or irradiated to enhance color properties; these are common and generally permanent treatments, unlike dyeing or coating a stone which can show wear with time and exposure to sunlight. As a general guideline: if the color looks too bright to be natural, it's probably not! I make a note of any treatments that I know of applied to materials. In earlier days, I was drawn to dyed chalcedony stones because of their vibrant colors, only to be disappointed as this color faded - especially with exposure to sunlight - and I was left with a bunch of dirty-hued rocks. Now, I tend to avoid dyed stones and I cast a wary eye on dyed pearls, though they tend to fare better with time and wear.

I'm a physicist by trade, so I relate to color in terms of its place in the electromagnetic spectrum in addition to finding colors aesthetically pleasing. References from color theory and physics textbooks coexist peacefully in my color pages. The graphic below is a standard image depicting visible light (what we can see) relative to the electromagnetic specturm.

In natural daylight, what we see is reflected light from the sun, and the sun emits different intensity of light at different wavelengths; this is the solar spectrum. When a lightbulb claims to be like natural light, it means the spectrum of its emitted light is similar to the solar spectrum. The peak of the solar spectrum can be estimated by Wien's law, which is a formula that relates a source's surface temperature to the wavelength at which more power is emitted than at any other wavelength. The sun's surface temperature is around 5500K, which leads to a peak wavelength around 500nm, which is near the center of what we call visible light. Very cool.