Denver gem & mineral showcase - gems on display

A display case with gems of all colors and sizes, at the Denver Coliseum Show. © Addison Rice. Used with permission.

This year, Denver’s annual Gem and Mineral Showcase, comprised of twelve separate shows, was held from September 8-17th. With a wide variety of vendors, there was something for everyone. From dyed agate slabs and simple strands of freshwater pearls to rare fossils and trapiche gems, the diverse displays were almost as incredible as the pieces themselves. Here are a few trends and highlights from the show.

Purple Chalcedony (Grape Agate)

A recent find in Indonesia, purple chalcedony in botryoidal form took over the show. This material, actually marketed as “grape agate,” has a lovely form. High-quality specimens have a nice color and excellent sparkle.  Most of the material, however, is somewhat dull.

Denver gem & mineral showcase - grape agate

Purple chalcedony, often called grape agate, forms in a lovely botryoidal habit. © Used with permission.


Another popular rarity, tanzanite’s blue hues could be seen on many tables. Most of the rough was small with poor color saturation. Due to Tanzania’s ban on tanzanite rough export, there are never many large rough gems. However, a few pieces, exported before the ban, made it to the show.

Trapiche Emeralds and Rubies

A small selection of extremely rare trapiche gems were on display. A few small, opaque trapiche rubies were available at the Artisan Jade booth at the Colorado Mineral and Fossil Fall Show. In addition, AA Colombian Emeralds at the Denver Coliseum Show and New Era Gems at the Denver Mineral Show each had a couple dozen trapiche emeralds.

Denver gem & mineral showcase - trapiche emeralds

Trapiche emeralds at the AA Colombian Emeralds booth, Denver Coliseum Show. © Addison Rice. Used with permission.

Gold Sheen Sapphires

Unique to a mine in northeastern Kenya, these untreated specimens of corundum exhibit a beautiful sheen. This sheen arises because hematite or ilmenite inclusions formed as dense platelets or needles. These gems, displayed at the Goldsheen Sapphires booth at the Denver Mineral Show, can have a yellow, red, or blue body color.

Denver gem & mineral showcase - goldsheen sapphire

22.2-ct “Goldrush” goldsheen sapphire. © Goldsheen Sapphires. Used with permission.

Blue Amber

There was a lot of amber around, some red, some yellow, some nearly colorless, and many with insects. However, the amber at the Indogems booth was more unique. Blue amber, found in Indonesia, the Dominican Republic, and Mexico, is a rare gem. The blue color, only present in amber from the extinct Hymenaea protera tree, is a result of surface fluorescence under ultraviolet light. In fact, perylene, an aromatic hydrocarbon, is the chemical responsible for this fluorescence. When incandescent light shines through these gems, the internal yellow to red color is visible. The Usambara effect, where the path length of light alters the color seen, is also present in these ambers.

Denver gem & mineral showcase - blue amber

The body color and blue surface fluorescence of blue amber is hypnotizing. © Used with permission.

Rainbow Lattice Sunstone

Discovered in 1985, rainbow lattice sunstone from the Harts Range in Australia exhibits beautiful patterns and iridescence. Another rare gem, this is a moonstone with inclusions of hematite and ilmenite, creating the unique iridescent lattice with parallel lines and equilateral triangles visible.

denver gem & mineral showcase - rainbow lattice sunstone

An 11.09 ct rainbow lattice sunstone. © Rainbow Lattice Sunstone. Used with permission.

Other Rare Gems

Of course, many other rarities were on display. Lapidaries purchasing rough sought out grape garnets, which are rapidly gaining popularity, and bright orange spessartites. In addition, a bit of searching revealed a few cat’s eye jades, star sapphires, and alexandrites. The main show, themed “Gold and Silver” for its 50th anniversary, had an abundance of rare minerals, with fantastic crystalline specimens of gold and silver on display.