Spessartine
Spessartine is the manganese garnet, Mn2+3Al2(SiO4)3: cubic, hardness 7 to 7.5, density 4.190, n 1.800. Its Kinko analysis works out at 97% Mn at the X site.
Spessartine is the manganese garnet, Mn2+3Al2(SiO4)3 on both the IMA list and the Handbook sheet: cubic, hardness 7 to 7.5, density 4.190, one refractive index of 1.800, no cleavage, in red, orange, yellow and brown. It forms a series with almandine, and the name follows whichever of manganese or iron dominates the garnet's X site.
In short
- One species in a group. The September 2026 IMA-CNMNC Master List lists spessartine as Mn2+3Al2(SiO4)3, status G, 1832, Germany. Grew and co-authors, American Mineralogist 98 (2013) placed it in the garnet group with 13 other species, and gives its end-member as {Mn2+3}[Al2](Si3)O12. GIA calls it the orange garnet, and the International Gem Society says spessartite and spessartine are both accepted spellings; the IMA list has a row only for spessartine.
- The X-site rule. An aluminium garnet is named for the cation that dominates its X site: manganese makes spessartine, iron almandine, magnesium pyrope, calcium grossular. The IMA garnet report draws the divisions this way. Worked from the sheets: the Kinko mine, Japan analysis is 97.0% manganese at X; almandine’s Falun analysis is 81.5% iron.
- Why a refractometer cannot apply the rule. The X site holds four common cations, so three proportions are free. A refractometer and a scale give two numbers, n and density, and two numbers cannot fix three unknowns. Spessartine’s 1.800 and almandine’s 1.830 are end-member values; a mixed garnet between them needs an analysis to be named.
- A documented discrepancy: water. The Kinko analysis prints 0.86% H2O. The IMA garnet report says water in spessartine has not been reported above 0.64 wt%, apart from one 2.5 wt% value it calls anomalous. The sheet does not say how its water was measured; we print both.
- A pegmatite garnet, on the sheet: common in granite pegmatites, granites and rhyolites, with rhodonite, topaz, beryl and tourmaline among its associates. Its Distribution names Aschaffenburg in the Spessart, Broken Hill, and Nangue and Urucum in Minas Gerais.
| Dominant X cation | Species (IMA formula) | n on the sheet | Density, measured | Cell edge a | 20.00 g piece in water | Sheet analysis, X-site share worked |
|---|---|---|---|---|---|---|
| Manganese (Mn2+) | Spessartine, Mn2+3Al2(SiO4)3 | 1.800 | 4.190 | 11.621 | 15.23 g | Kinko mine, Japan: Mn 97.0%, Ca 3.0% |
| Iron (Fe2+) | Almandine, Fe2+3Al2(SiO4)3 | 1.830 | 4.318 | 11.526 | 15.37 g | Falun, Sweden: Fe 81.5%, Mg 15.4%, Mn 2.0%, Ca 1.2% |
| Magnesium | Pyrope, Mg3Al2(SiO4)3 | 1.714 | 3.582 | 11.459 | 14.42 g | Dora-Maira, Italy: Mg 2.87, Fe 0.05, Ca 0.02 (as printed) |
| Calcium | Grossular, Ca3Al2(SiO4)3 | 1.734 | 3.594 | 11.851 | 14.44 g | Georgetown, California: Ca 3.00, Fe 0.02 (as printed) |
| Spessartine minus almandine | The series the sheets name | −0.030 | −0.128 | +0.095 | −0.14 g | Two measurements, three free proportions: an analysis decides |
What is spessartine? The manganese garnet
The names. The September 2026 IMA-CNMNC Master List writes spessartine Mn2+3Al2(SiO4)3, status G, with the year 1832, the country Germany, and a first reference to the second edition of Traité Élémentaire de Minéralogie, Paris, 1832. The Handbook sheet prints the same formula, the group line Garnet group and the Name field for the locality near Spessart, Germany. The IMA garnet report says the mineral was recognised by M.H. Klaproth in 1797 and that the name spessartine was introduced by F.S. Beudant in 1832.
Spessartite or spessartine? The International Gem Society says British gemmologists preferred the -ite ending and American ones -ine, and that both are now accepted. On the IMA list a script finds a row for spessartine and none for spessartite, almandite or the trade names mandarin and malaia. GIA writes spessartine (also called spessartite) is an orange garnet.
What it looks like, per the sheet. Cubic; commonly euhedral dodecahedra or trapezohedra, alone or with other cubic forms, to 10 cm; also granular and massive. Red, reddish orange, yellow, yellowish brown, reddish brown, brown or black, pale pink to pale brown only in thin section. White streak, vitreous lustre, no cleavage recorded, fracture uneven to conchoidal, hardness 7 to 7.5.
Is my garnet spessartine or almandine? The X-site rule
The X-site rule: a garnet with aluminium at its Y site is named for the cation that dominates its X site. Grew and co-authors, American Mineralogist 98 (2013) draw the garnet group’s divisions on the occupancy of the X site, with calcium, magnesium, manganese and iron at the corners, and say the dominant-constituent and dominant-valency rules are what identify species. Manganese-dominant is spessartine; iron-dominant, almandine.
Worked on the sheet. The Kinko mine, Yamaguchi Prefecture analysis reads SiO2 35.33, Al2O3 21.50, MnO 41.06, CaO 1.02, H2O 0.86, with traces of TiO2, FeO and MgO, total 99.77. On 12 oxygens, leaving the water out, the X site is manganese 2.89 and calcium 0.09: 97.0% manganese. The sheet prints Mn2.82 Ca0.09 on a basis of three tetrahedral cations, which is 96.9%: the same answer. Manganese is 31.80% of the analysis by mass against 33.29% in the end-member. The International Gem Society says spessartite has been found up to 95% pure; that is a purity of the whole garnet, where 97.0% is the X site alone, so the two figures measure different things.
The documented negative. The sheets put spessartine at n = 1.800 and almandine at 1.830, and a scale separates them by 0.14 g on a 20.00 g piece. But the X site has four common cations: three proportions to find, and a refractometer and scale give two numbers. Pyrope and grossular sit lower than both on their sheets for index and density, so magnesium or calcium in the mix pull a reading down, and an almandine with some pyrope in it can read where an iron-bearing spessartine would. Between 1.800 and 1.830, name it spessartine–almandine garnet until an analysis says which cation leads. The almandine side of the same arithmetic is on almandine.
How much water can spessartine hold? A documented discrepancy
The sheet’s number. The Kinko mine analysis prints 0.86% H2O in a total of 99.77. Its formula line gives the tetrahedral site as silicon 2.86 and aluminium 0.14, short of three silicon, and the sheet prints no hydrogen in that formula.
The report’s number. Grew and co-authors, American Mineralogist 98 (2013) says water contents in pyrope, almandine and uvarovite are reported not to exceed 0.3 wt% and, in spessartine, not above 0.64 wt%, and that a reported 2.5 wt% H2O in spessartine is anomalous and needs confirmation. The 0.86% on the sheet is above that ceiling. We do not resolve it: the sheet does not say how the water was determined.
Why it matters to a label. Nothing here changes the name: at 97.0% manganese the Kinko garnet is spessartine whatever the water. It is a reason to read an old printed analysis as a record of what was measured, not as a structural formula. The vocabulary for such labels is on what is a type locality.
Where spessartine is found: the Spessart, Broken Hill and Minas Gerais
The Occurrence field: common in granite pegmatites, granites and rhyolites, and formed in some skarns and metasomatic manganese-rich rocks next to intrusions or in regionally metasomatised areas. The Association line names quartz, potassic feldspar, tourmaline, rhodonite, pyroxmangite, tephroite, alleghanyite, galaxite, muscovite, topaz, apatite, beryl, albite, bixbyite and pseudobrookite. Rhodonite and spessartine on one piece are compared on is rhodonite a garnet.
The Distribution field opens while a less-common garnet, nevertheless many localities and names: Aschaffenburg, Spessart Mountains, Bavaria, Germany; Seriphos, Cyclades, Greece; Leiper’s quarry, Avondale, Pennsylvania; the Rutherford mine, Amelia, Virginia; the Ramona and Pala districts, California; the Thomas Range, Utah; Ely, Nevada; near Nathrop, Colorado; Nangue and Urucum, Minas Gerais, and Carnaúba near Picui, Rio Grande do Norte, Brazil; Marienflüss, Namibia; Tsilaizina and Anjanabonoina, Madagascar; the Gilgit district and Dusso, Pakistan; Broken Hill, New South Wales; and the Wada-toge Pass, Japan.
In Britain the sheet names nothing, and we add nothing. The rest of the reference section is at the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.