Spessartite, also spelled spessartine, is the manganese aluminum member of the garnet group. It is the orange garnet, ranging from yellowish orange through pure orange to reddish orange and brownish red. The brightest stones, sold as mandarin garnet, came first from Namibia in the 1990s and later from Nigeria. Spessartite is one of the few gems with a strong, natural orange color and no need for treatment.
What spessartite is
Spessartite has the ideal formula Mn3Al2(SiO4)3, with manganese in the X site and aluminum in the Y site. It belongs to the pyralspite series of garnets along with pyrope and almandine. Most natural spessartite contains some almandine, and iron from that almandine pushes the color toward red and brown. The purest, most manganese-rich stones show the cleanest orange.
The name comes from the Spessart, a forested mountain range in Bavaria, Germany, where the mineral was first described in the nineteenth century. Gemologists use both "spessartite" and "spessartine"; the International Mineralogical Association lists the species as spessartine.
Spessartite is cubic and singly refractive. Its refractive index of about 1.79 to 1.82 is high, giving bright luster and good brilliance, and it is often above the limit of a standard refractometer. It is dense, with a specific gravity near 4.1 to 4.2. Hardness runs 6.5 to 7.5, and it has no cleavage.
Color
Manganese is the main coloring element and is part of spessartite's own chemistry. That makes the orange color stable and natural. The most valued color is a vivid, pure orange sometimes compared to the skin of a mandarin or to a Fanta soda. Stones with more iron look reddish orange, brownish orange or brownish red. Under incandescent light, orange garnets look warmer; in daylight they may show a slight yellow tint.
Spessartite is almost never treated. Some reports mention heating, but it is not a routine practice, and the color does not need it. The color in gemstones page covers manganese as a chromophore.
Mandarin garnet from Namibia and Nigeria
In the early 1990s, a deposit in the Kunene region of northwestern Namibia, close to the Angolan border, began producing intensely orange spessartite. The material was sold as mandarin garnet and quickly drew attention for its bright, pure color. The Namibian deposit lay in a remote area and produced inconsistently.
Later in the 1990s, Nigeria began producing similar orange spessartite from pegmatites. Nigerian material ranges from yellowish to reddish orange, with some fine, clean stones. Since then, Madagascar, Tanzania (Loliondo), Kenya and Mozambique have also produced bright orange spessartite. "Mandarin" is a trade name for color rather than a guarantee of origin.
Other sources
Spessartite has also come from Brazil (Minas Gerais), Sri Lanka, Pakistan, Afghanistan, China, Myanmar, Australia and the United States. California's Ramona district and Virginia's Amelia pegmatites produced fine specimens in the past. Pakistani and Chinese crystals are often prized by mineral collectors as well-formed crystals on matrix.
How spessartite forms
Most gem spessartite forms in granite pegmatites, coarse-grained igneous rocks that become rich in manganese and other rare elements in their late stages. It often grows with tourmaline, quartz and feldspar in pegmatite pockets. Spessartite also forms in some manganese-rich metamorphic rocks. The igneous rocks and gemstones page explains pegmatites, and the rock cycle page puts them in context.
Clarity
Spessartite is often included. Typical inclusions are wavy, lace-like fluid inclusions and healed fractures with a "shredded" look, plus small needles and crystals. Clean stones exist, especially from Nigeria and Namibia, and command higher prices. Buyers generally accept minor inclusions in spessartite that would not be visible face-up.
Pyrope-spessartite blends
Pyrope-spessartite mixtures produce two interesting garnets:
- Malaya garnet, from the Umba Valley on the Kenya-Tanzania border, ranges from pinkish orange to reddish orange and peach. The name comes from a Swahili word often translated as "outcast," because miners first found it among rhodolite and could not place it.
- Color-change garnet, also from East Africa and Madagascar, contains vanadium and chromium and shifts from bluish green or gray in daylight to purplish red under incandescent light.
These blends sit between spessartite and pyrope, and gemologists separate them by refractive index, density and spectrum. The almandine garnet page covers the related pyrope-almandine blend called rhodolite.
Identification
Spessartite can look like orange sapphire, hessonite, orange zircon, fire opal or imperial topaz. Its single refraction, high refractive index and manganese absorption lines in the violet and blue, seen with a hand spectroscope, separate it. Hessonite, the orange grossular, has a lower refractive index and a swirled internal texture. The how to identify gemstones guide explains these tests.
Value
Value depends mostly on color. A pure, saturated orange with no brown is the most valued. Size matters too: clean stones over 5 carats with fine color are uncommon. Because spessartite is untreated and very bright, it has a following among colored stone buyers looking for something different from more familiar gems.
Wear and care
Spessartite is hard enough for rings, earrings and pendants and has no cleavage. Heavily included stones are a little more prone to breaking from hard knocks. Clean with warm soapy water and a soft brush. Ultrasonic cleaning is usually safe for clean stones but best avoided for those with many inclusions. Avoid sudden temperature changes. More detail is in the jewelry cleaning guide.
Frequently asked questions
What is mandarin garnet?
Mandarin garnet is a trade name for bright orange spessartite, first from Namibia in the early 1990s and later from Nigeria and other African sources.
Is spessartite the same as spessartine?
Yes. Both names refer to the same manganese garnet species. Mineralogists use spessartine, and the gem trade often uses spessartite.
Is spessartite treated?
Spessartite is rarely treated. Its orange color comes from manganese in its chemistry and is natural and stable.
Is spessartite a January birthstone?
All garnets are January birthstones, including orange spessartite.