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Trick Gems at Walters & Hogsett in Boulder, Colorado

Trick Gems

In celebration of Halloween, this week we are bringing you four gemstones that have some tricks up their sleeves! Tricks, in the world of gemstones, are called phenomena, which basically means that the gemstone will display unusual optical effects when light interacts with it. Phenomena can be anything from complete color change to the magical appearance of a star, and many surprises in between! Keep on reading to learn about a few of our favorites.


Star Sapphire (Corundum)
Labradorite is a phenomenal gemstone that has become very popular in fashion jewelry. When light strikes this often grayish blue stone, it displays a bright flash of blue and green, called “labradoresence.”Labradorite gets its name from the German meaning of “Field Stone” and is a member of the mineral Feldspar. While the stone is common, gem quality Labradorite that displays a striking flash of Labradorescences is rare. This gemstone is often seen cut into a cabochon shape, meaning flat on the bottom and domed on top to maximize the optical illusion!


Star sapphires are the phenomenal variety of the mineral species corundum that display a star effect called “asterism” when hit with a direct light source. These beauties can be found in many colors including purple, plum, violet-ish blue, blue, greenish blue, gray, and dark tones of brown and green. The star appears as a contrasting lighter color within the stone, often showing six-rays. Rarely, one will find a twelve-ray star, usually seen in darker stones. Similar to Labradorite, Star Sapphires are often cut into cabochons to enhance the appearance of the star. If you are wondering how these stars are possible, the answer is simple! Each one is the effect of intersecting rutile needlethat formed inside the stone when it was growing!

Cat's-Eye Chrysoberyl


Cat’s-Eye Chrysoberyl is one of the rarest and most valuable phenomenal gemstones, which displays a phenomena called “chatoyancy,” appearing as a single ray straight through the stone …similar to a cat’s eye, hence the name! In its finest quality, the chatoyancy is referred to as “milk and honey” where when a light source is directed at the side of the stone, one side of the eye will be a milky color and opposite side will remain gold. When the stone is rotated, the colors switch. The chatoyancy in Chrysoberyl is a result of fine hollow needlerunning through the stone and when those are exposed to a light source a ray appears perpendicularly to those inclusions!


As if chrysoberyl didn’t already surprise us enough, let’s chat about what else it can do! Alexandrite is the color change version of the mineral species Chrysoberyl in it’s transparent quality. Often described by gem aficionados as “emerald by day, ruby by night,” alexandrite was originally discovered in Russia’s Ural Mountains in the 1830s, but it’s now found in Sri Lanka, East Africa, and Brazil. Fine material is exceptionally rare and valuable. Alexandrite, with its chameleon-like qualities, can be a lovely green in daylight or fluorescent light, changing to brownish or purplish red in the incandescent light from a lamp or candle flame. This is a result of the complex way the mineral absorbs light. Alexandrite is also a strongly pleochroic gem, which means it can show different colors when viewed from different directions. Typically, its three pleochroic colors are green, orange, and purple-red. However, the striking color change doesn’t arise from the gem’s pleochroism, but rather from the mineral’s unusual light-absorbing properties.

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