Rhodonite
Rhodonite is a pink manganese silicate, hardness 5.5 to 6.5, density 3.57 to 3.76. IMA formula: one calcium per five silicon; the Handbook analysis: 0.26.
Rhodonite is a pink manganese silicate: triclinic, hardness 5.5 to 6.5, density 3.57 to 3.76, two perfect cleavages at 92.5 degrees, white streak, its exterior often black with manganese oxides. The IMA list writes it CaMn3Mn(Si5O15), redefined in 2019, beside the Handbook's (Mn2+,Fe2+,Mg,Ca)SiO3; Germany is its country of first discovery.
In short
- Two formulas, both shown. The September 2026 IMA-CNMNC Master List gives CaMn3Mn(Si5O15), status Rd (redefined), 2019 s.p., with Germany as the country of first discovery. The Handbook of Mineralogy sheet, dated 2001, prints (Mn2+,Fe2+,Mg,Ca)SiO3. Worked on standard atomic weights, the IMA formula is 34.32% manganese by mass, the figure the live rhodochrosite and rhodonite page uses.
- The calcium check. The IMA formula holds one calcium for every five silicon atoms, 8.76% CaO by mass. The sheet’s only analysis, from Chikla, Maharashtra, India, has 2.25% CaO: 0.26 calcium per five silicon plus aluminium, worked from the oxides. That is too little to fill even half of the one site the IMA formula gives to calcium.
- Three IMA rows share rhodonite’s Si5O15 unit. A script over the list finds rhodonite, ferrorhodonite (CaMn3Fe, 2016, Australia) and vittinkiite (MnMn3Mn, 2017, Finland). Vittinkiite’s formula adds up to MnSiO3, the same as pyroxmangite’s, so an analysis alone cannot name a manganese pyroxenoid.
- The home tests are on other pages. Hardness, a broken edge and a refractometer reading near 1.73 are set out on how to tell if rhodonite is real; garnet on is rhodonite a garnet. A 20.00 g piece weighs 14.40 to 14.68 g in water, and pyroxmangite overlaps it.
- Gem crystals at Broken Hill and Morro da Mina, on the sheet. Its Distribution field also names Franklin and Sterling Hill, New Jersey, and the Meldon quarry, Okehampton, Devon. The bustamite sheet names a Meldon quarry too, so a Devon label does not settle which pink silicate it is.
| Name | Formula and source | IMA status, year, country | Calcium per 5 Si | Manganese per 5 Si | Iron per 5 Si | What the numbers decide |
|---|---|---|---|---|---|---|
| Rhodonite | CaMn3Mn(Si5O15), IMA | Rd, 2019 s.p., Germany | 1 | 4 | 0 | The reference point: 8.76% CaO, 34.32% Mn by mass |
| Ferrorhodonite | CaMn3Fe(Si5O15), IMA | A, 2016-016, Australia | 1 | 3 | 1 | Iron where rhodonite has its fifth manganese: 11.21% FeO, worked |
| Vittinkiite | MnMn3Mn(Si5O15), IMA | A, 2017-082a, Finland | 0 | 5 | 0 | Manganese where rhodonite has calcium; 54.14% MnO |
| Pyroxmangite | Mn2+SiO3, IMA | G, 1913, USA | 0 | 5 | 0 | Same composition as vittinkiite; different structure and sheet cell |
| Bustamite | Mn2Ca2MnCa(Si3O9)2, IMA | G, 1826, USA | 2.5 | 2.5 | 0 | Far more calcium; its sheet says the pink fades in light |
| Chikla, India: the Handbook rhodonite analysis | 2.25% CaO, 50.54% MnO, 0.96% FeO, 0.55% MgO | Analysis printed on the 2001 sheet | 0.26 | 4.68 | 0.09 (magnesium 0.09) | Below 0.5 calcium: not enough to fill half the calcium site |
What is rhodonite? A manganese silicate with two formulas
The names. The September 2026 IMA-CNMNC Master List lists rhodonite as CaMn3Mn(Si5O15), status Rd, which the list defines as an existing mineral redefined during the IMA era, with the year 2019 s.p. Its country column, the country of first discovery, reads Germany. The Handbook sheet prints (Mn2+,Fe2+,Mg,Ca)SiO3 and gives the name as from the Greek for rose, for its colour. Both formulas are shown on this site because they differ: the IMA one fixes calcium in the structure, the Handbook one lists it as a substituting cation.
What it looks like, per the sheet. Triclinic, point group -1. Crystals are rough, with rounded edges, typically tabular and elongated along [001], to 20 cm; the material is commonly massive, cleavable to compact. Colour is rose-pink to brownish red, grey or yellow, the exterior commonly black from manganese oxides, with a white streak and a vitreous lustre, somewhat pearly on cleavages. Cleavage is perfect on {110} and {1-10}, meeting at 92.5 degrees, and good on {001}, read from the rendered sheet; reading a broken edge is covered on cleavage or fracture.
Where it forms. The Occurrence field: in manganese-bearing deposits formed by hydrothermal, contact and regional metamorphic, and sedimentary processes. Its listed associates include calcite, willemite and franklinite at Franklin, New Jersey, and tephroite, galaxite and magnetite at Bald Knob, North Carolina.
Does the Handbook analysis fit the 2019 formula? The calcium check
The rule, as arithmetic. CaMn3Mn(Si5O15) has one calcium for every five silicon atoms. On standard atomic weights (Ca 40.078, Mn 54.938, Si 28.085, O 15.999) the formula mass is 640.24, and the ideal composition is 8.76% CaO, 44.32% MnO and 46.92% SiO2. A rhodonite analysis should carry close to one calcium per five silicon; much less, and the calcium site cannot be calcium-dominant.
Worked on the sheet. The Chikla, Bhandara district, Maharashtra analysis reads SiO2 45.46, Al2O3 0.27, FeO 0.96, MnO 50.54, MgO 0.55, CaO 2.25, total 100.03. Dividing each oxide by its formula mass and scaling to five silicon plus aluminium gives calcium 0.26, manganese 4.68, iron 0.09 and magnesium 0.09. The sheet’s own one-silicon formula, Mn0.93 Ca0.05 Fe0.02 Mg0.02, says the same. To reach one calcium per five silicon at this silica content the analysis would need about 8.55% CaO; it has 2.25%.
What that does and does not mean. The sheet is from 2001; the IMA redefinition is dated 2019 and vittinkiite was approved in 2017, so the sheet could not apply either. We do not relabel the Chikla material: naming it needs the crystal structure, not one analysis. The check is a reason to read an old analysis, or an old label, as rhodonite in the 2001 sense. The manganese content is consistent with the 39.14% the live rhodochrosite comparison page works from the same analysis.
Rhodonite, ferrorhodonite, vittinkiite or pyroxmangite? What the IMA list separates
Method and count. Every line of the September 2026 IMA list, saved as text with pdftotext -layout, was parsed by script into name and formula (controls: the rhodonite, topaz, quartz and beryl rows must parse), and an independent scan of the raw lines checked the result. Three rows are written with Si5O15: rhodonite, CaMn3Mn; ferrorhodonite, CaMn3Fe, A, 2016-016, Australia; and vittinkiite, MnMn3Mn, A, 2017-082a, Finland. Eleven more rows are written with Si5O14, among them babingtonite, marsturite and nambulite.
A documented negative. Vittinkiite’s formula adds up to five MnSiO3; pyroxmangite’s IMA formula is Mn2+SiO3. The same composition in two structures means a chemical analysis alone cannot say which of the two a piece is, and a rhodonite-shaped analysis low in calcium, like Chikla’s, sits between rhodonite and both of them. The Handbook sheets show the structural difference in their cell data: rhodonite c = 12.205, pyroxmangite c = 17.391. That is X-ray work, not a home test.
The practical look-alikes. Pyroxmangite matches rhodonite on hardness (5.5 to 6), density (3.61 to 3.80) and cleavage angle (92 degrees) on its sheet. Bustamite, (Mn2+,Ca)3Si3O9 on its sheet, is pale pink to brownish red on its sheet, lower in density (3.32 to 3.43) and, its sheet says, its pink colour fades on exposure to light. The home sequence for these is on how to tell if rhodonite is real and the carbonate on rhodochrosite; neither page’s rule is repeated here.
Where rhodonite is found: Broken Hill, Franklin, Meldon and Morro da Mina
The Distribution field opens a few localities for studied or fine material and names: around Yekaterinburg, Ural Mountains, Russia; the Harstigen mine near Persberg, and Långban, Värmland, Sweden; Băiţa and Cavnic, Romania; near Viu and St. Marcel, Val d’Aosta, Italy; Broken Hill, New South Wales, as gem crystals; the Noda-Tamagawa mine, Iwate, and many other places in Japan; Franklin and Sterling Hill, New Jersey; Bald Knob, North Carolina; Butte, Montana; Morro da Mina, Conselheiro Lafaiete, Minas Gerais, as gem crystals; and the Chiurucu mine, Peru.
In Britain the sheet names one place: the Meldon quarry, Okehampton, Devon. The bustamite sheet names the Railroad quarry, Meldon, near Okehampton, and the Treburland mine in Cornwall. A pink silicate labelled Meldon may be either species; the bustamite sheet’s light-fading note makes the difference worth knowing. We add no locality the sheets do not name.
Broken Hill appears on the rhodonite, pyroxmangite and bustamite sheets, so a Broken Hill label narrows nothing among the three. 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.