23ct Rhodolite, 20ct Tsavorite and 32ct Spessartite Garnets
Photo by: Mark Mauthner

The name “garnet” is derived from the Latin “granatus”, referring to the resemblance garnet crystals share with pomegranate seeds

Garnet has a history of appreciation dating back thousands of years, from the time of the Egyptian pharaohs to the Greco-Roman period and through the Middle Ages. It was one of the most favored gems of religious, political and social leaders to signify status

The garnet group of gems is made up of the end-members pyrope, almandite, spessartite, grossular and andradite

Deep red Bohemian pyrope garnets, discovered in the early 16th century, helped increase availability of garnet for the middle class, and thus made it a more mainstream gem until the late 1800’s

Fun Fact: the word “pyrope” stems from the Greek words meaning “fire eye”

40.66ct Rhodolite from Tanzania
Photo by: Robert Weldon

Rhodolite garnets are a pyrope-almandine mixture that range in color from purple to purplish-red. This 40.66ct purple rhodolite from Tanga, Tanzania, is an extremely large example of this material

Grossular Garnet Rough and Cut
Photo by: Jeff Scovil

Garnet has a high to very high refractive index range, from pyrope and grossular at approx ~1.74 to rhodolite at ~1.76 to spessartite at ~1.80 and andradite at ~1.88. Gemologists use refractive index, specific gravity, absorption spectra and inclusions to differentiate garnet’s end-members and varieties

8ct Tsavorite
Photo by: Robert Weldon

Tsavorite is the rich green variety of grossular garnet discovered by Campbell Bridges in 1967 in Tanzania, and again 3 years later in Kenya

Demantoid Garnets from Ural Mountains in Russia
Photo by: Robert Weldon

Andradite garnets range in color from brown to the vivid green of highly sought after Russian demantoids. The cause of this vivid green color is due to trace amounts of chromium, while iron gives it a more yellowish appearance. The discovery of Russian demantoid garnet in 1854 added an exciting new color variety to the garnet family, which designers eagerly embraced. The initial source was quickly depleted but left a lasting mark on the industry that allowed for its resurgence when material reentered the market after the Cold War. Today, commercial quantities of demantoid are available from Russia, Namibia and Madagascar

Fun Fact: Andradite’s dispersion is 0.057, which is higher than that of a diamond at 0.044

Demantoid Crystal in Matrix
Photo by: Jeff Scovil

Garnets typically form under metamorphic or metasomatic conditions in which preexisting igneous or sedimentary rocks are altered by heat and pressure due to tectonic forces or contact with an igneous intrusion

Red hessonites (above right), a variety of grossular, enjoyed increased production in recent years from Southern Sri Lanka, providing a more affordable alternative to red spessartite

Spessartite Garnet Crystals and Gems from Tanzania & Nigeria
Photo by: Jeff Scovil

Gem quality spessartite crystals are found within metamorphosed schists. These crystals occur as euhedral or subhedral rhombic dodecahedrons (24 faces) which can sometimes look almost spherical

Namibian “Mandarin” Spessartites ranging from 0.92ct to 10.25ct

These vivid orange spessartites are extremely rare, usually occurring in sizes less than one carat. They were discovered by a farmer in 1992 along the Namibian border with Angola. The cause of this remarkable color is Manganese

12.18ct Malaia Garnet

Malaia garnets are a pyrope-spessartine mixture that often exhibit a color shift or even a color change, like the gem above. Recent increase in supply from Tanzania and Madagascar has helped make this a popular garnet in contemporary jewelry design

33.63ct Rainbow Garnet

Rainbow garnet from Alamos Mexico, New Mexico and Japan exhibits a play of color due to an outer layer of growth that creates diffraction grating-like interference colors

A new variety of garnet was discovered in Mali, West Africa, in 1994. Grossular-andradite, known in the trade as “Grandite Garnet” or “Mali Garnet”, has a chemical composition of (Ca,Fe)3Al2(Si04)3 and a refractive index range of 1.752 – 1.782. The color of most of the material ranges from yellowish-green to rich green to brown

Click below to see the Gems & Gemology, Fall 1995, article co-authored by Edward Boehm

Gem-Quality Grossular Andradite: A New Garnet From Mali


Violetish-Blue and Green Tanzanite (11 – 23ct)
Photo by Robert Weldon

Celebrating December’s Birthstone

Maasai traditions associate the color blue with new life, so it is only fitting that tanzanite, a stone discovered by Maasai herders in 1967, is the traditional gift for new mothers. It is, truly, the ultimate Birthstone.

A relative newcomer to the gem world, tanzanite has made a lasting mark on the jewelry industry. Mined only in one small area of a few kilometers in the Merelani hills, approximately 70 km Southeast of Arusha and Northwest of Mount Kilimanjaro, this rare stone is coveted by collectors and jewelers alike.

The rarest color of tanzanite is green, colored by trace amounts of chromium. Discovered in 1991, the local miners called it “combat”
because of its yellowish-green to bluish-green color. It is still considered one of the most collectable gems from Tanzania.

Read more about green tanzanite in this article by Edward Boehm and Dr. Barot – Gems and Gemology, Spring 1992

Maasai Warriors

Tanzanite was discovered in 1967 when wildfires engulfed the Merelani hills at the foot of Mount Kilimanjaro, naturally heat treating the material and exposing their striking blue-violet color.  A group of Maasai herders saw the exquisite stones and reported their findings to Portuguese geologist, Manuel D’Souza, who introduced this new discovery to the western world.

Tanzanite and Tsavorite Crystals
6ct Blue Tanzanite

Tanzanite’s strong pleochroism causes it to display a multitude of colors, primarily blue and violet. Depending on the lighting, a single gem can present as blue, violet and burgundy. This is due to the trace amounts of vanadium and/or chromium present during its formation. As with many gems, larger stones tend to appear in a deeper color than their small counterparts.

Independent artisanal miners in Block D 

Most tanzanite has to be heated to improve its color, which reduces or removes its reddish brown properties or improves color saturation.  Recently, natural color material has gained favor because of the strong pleochroic colors that can be manifested through skillful cutting.

8ct Pink Tanzanite


9.30ct Red Topaz

Like ruby, precious topaz gets its color from trace amounts of chromium (Cr+3). There are two theories as to how topaz derived its name. Some say it is named for the island of Topazios in the Red Sea, which historically produced peridot, while others believe it comes from the Sanskrit word tapaz or topas, meaning “fire”

Ancient Egyptians believed that topaz was colored by the golden glow of the sun god Ra.  Ancient Romans associated the stone with Jupiter, also god of the sun.  These myths were likely fueled by the gem’s array of fiery hues

8.24ct Pink Topaz from Brazil
RareSource selection of pink to red topaz ranging from 9.06ct – 24.04ct

The color most often associated with topaz is yellow, but it is actually found in orange, brown, red, blue, pink, violet, and colorless as well. Until geologists started identifying differences in mineral specimens about 200 years ago, all yellow and golden gemstones were labeled as topaz

Imperial topaz was named after nineteenth century Imperial Russia, and was so rare and beautiful that ownership of the gem was only granted to the royal family and those fortunate enough to receive it as a gift from the Czar

Washing for gem topaz at the Bela Vista Mine, Ouro Preto, Brazil
Photo Credit: Sergio Castro

Topaz formed in hydrothermal veins and is found in heavily altered schist that has turned into lateritic clay.

Waterworn Red Topaz Crystal Rough
Photo Credit: Sergio Castro

The Capão do Lana Mine, just outside of the village of Rodrigo Silva in Minas Gerais, Brazil, once produced the largest amount of imperial topaz worldwide. Mineral deposits were first recorded by the Portuguese in this location in 1751, and in 1768, they were discovered to contain topaz. The Capão Mine recently stopped operating but the Vermelhão, Dom Bosco, Boa Vista and Bela Vista are still producing. Read more about Brazilian Topaz in this article by Edward

See the amazing 48.86ct “Whitney Flame” red topaz in the Gem Hall of the Natural History Museum at the Smithsonian Institute in Washington DC


32.44ct Liddicoatite Tourmaline named in honor of Mr. Richard T. Liddicoat, former president of GIA
Photo by R. Weldon

Introduced to Europeans in the 1700’s, Tourmaline became known as the Muse’s stone and is said to assist in the creative flow of artists across many mediums

44.39ct Bi-Color Tourmaline

Fun Facts
Tourmaline contains pyro-electric properties. The Dutch discovered tourmaline’s ability to attract dust and ash when heated, and used the long, slender crystals to clean their meerschaum pipes by drawing out the ashes

Today this property, creating strong polarity, is used in hair styling tools

Tourmalines also have a piezoelectric effect that was first applied in underwater sonar systems and ultrasound technology
during the second world war

Teal Tourmaline 2.39ct – 9.44ct

 Tourmaline’s strong pleochroism, which means that the color appears differently based on the direction in which it is viewed, requires great skill in cutting to optimize the face-up color

Renewed artisanal mining activity in the Araçuai-Salinas district (made famous in the 1970’s and 1980’s) is producing unique colors as seen above

Rubellite Tourmalines from the Cruzeiro Mine 2.82ct – 14.14ct

The Cruzeiro Mine has been commercially operational since the 1940’s when the US mined mica there during WWII for electronic components.  Since the 1950’s, it has produced fine quality rubellite, indicolite, bi-color and emerald green tourmalines 

Edward standing in a Tourmaline pegmatite pocket at the Cruzeiro Mine with renowned Brazilian geologist/miner Odulio Moura
4.49ct and 3.29ct Paraiba Tourmalines
Photo by R. Weldon

Tourmaline ranges dramatically in demand and value, and the most desired is the Paraiba tourmaline from Paraiba, Brazil.  A relative newcomer in the gemstone world, these brilliant blue and green elbaite tourmalines were discovered in the late 1980’s.  Because of their scarcity and electric colors, caused by trace amounts of copper and manganese, they are now one of the most coveted gemstones in the world