Is rhodochrosite the same as rhodonite
No. Rhodochrosite is manganese carbonate, hardness 3.5 to 4; rhodonite is a manganese silicate at 5.5 to 6.5. Their densities overlap, so a scale cannot choose.
No. Rhodochrosite is manganese carbonate, MnCO3, hardness 3.5 to 4, with one perfect rhombohedral cleavage; rhodonite is a manganese silicate, hardness 5.5 to 6.5, with two perfect cleavages at 92.5 degrees. Both are pink and both occur at Butte, Montana. Their densities overlap, 3.70 against 3.57 to 3.76, so hardness decides.
In short
- Carbonate against silicate. Rhodochrosite is MnCO3, 47.79% manganese by mass. Rhodonite is a manganese silicate whose formula the IMA redefined in 2019 as CaMn3Mn(Si5O15), 34.32% manganese; the Handbook sheet still prints (Mn2+,Fe2+,Mg,Ca)SiO3. Both are named from the Greek for rose.
- The 1.5-point rule. Rhodochrosite's hardness tops out at 4 and rhodonite's starts at 5.5. A steel point that bites easily is consistent with rhodochrosite; one that barely marks or skates is consistent with rhodonite or something harder.
- Weighing tells you nothing. Rhodochrosite's measured density of 3.70 sits inside rhodonite's 3.57 to 3.76. A 20.00 g piece weighs 14.59 g in water as rhodochrosite and 14.40 to 14.68 g as rhodonite.
- Cleavage agrees with hardness. Rhodochrosite breaks into rhombs on its perfect {10-11} cleavage. Rhodonite has two perfect cleavages meeting at 92.5 degrees plus a good third, and its exterior is commonly black from manganese oxides.
- Rhodochrosite bends light far more strongly. Its birefringence, 0.213, is the 12th widest of the 138 sheets in this site's 176-sheet reference set that print two or more refractive indices. Rhodonite's is 0.013 to 0.014.
| Criterion | Rhodochrosite | Rhodonite | Does it choose? |
|---|---|---|---|
| Chemical class | Carbonate | Silicate (pyroxenoid) | Yes, but not by eye |
| Formula, Handbook | Mn2+CO3 | (Mn2+,Fe2+,Mg,Ca)SiO3 | - |
| Formula, IMA list (Sept 2026) | Mn(CO3) | CaMn3Mn(Si5O15); redefined, 2019 s.p. | - |
| Manganese by mass | 47.79% ideal; 47.14% (Ljubija analysis) | 34.32% (IMA formula); 41.93% (MnSiO3 end-member); 39.14% (Chikla analysis) | Only by analysis |
| Hardness (Mohs) | 3.5 to 4 | 5.5 to 6.5 | Yes: 1.5 points apart |
| Cleavage | {10-11} perfect: rhombs | {110} and {1-10} perfect, at 92.5 degrees; {001} good | Yes, on a broken edge |
| Density, measured | 3.70 | 3.57 to 3.76 | No: they overlap |
| 20.00 g piece, weight in water | 14.59 g | 14.40 to 14.68 g | No |
| Birefringence (from printed indices) | 0.213 (1.597 to 1.810) | 0.013 to 0.014 (1.711 to 1.748) | Only on a refractometer |
| Crystal system; crystals | Hexagonal; rhombohedra and scalenohedra to 12 cm | Triclinic; rough tabular crystals to 20 cm | Yes, when crystals are present |
| Colour as recorded | Pink, rose-red, cherry-red, yellow, cinnamon-brown, may be banded | Rose-pink to brownish red, gray, yellow; exterior commonly black | Suggestive only |
Is rhodochrosite the same as rhodonite? No, and the formulas say why
Rhodochrosite is a manganese carbonate and rhodonite a manganese silicate. The Handbook of Mineralogy prints rhodochrosite as Mn2+CO3, in the calcite group, forming series with calcite and with siderite. Its rhodonite sheet prints (Mn2+,Fe2+,Mg,Ca)SiO3. The IMA-CNMNC list of minerals gives rhodochrosite as Mn(CO3) and rhodonite as CaMn3Mn(Si5O15), with status Rd, redefined, and the year 2019 s.p. The two sources are shown side by side here because they differ: the IMA formula fixes calcium as a structural component, and the Handbook sheet, dated 2001, treats it as one of four substituting cations.
Manganese content, worked. With Mn 54.938, C 12.011, O 15.999, Si 28.085 and Ca 40.078: MnCO3 has a formula mass of 114.946 and is 47.79% manganese. CaMn4Si5O15, the IMA formula, has a mass of 640.24 and is 34.32% manganese; the pure MnSiO3 end-member of the Handbook formula is 41.93%. The sheets' own analyses land where you would expect: 60.87% MnO from Ljubija, Bosnia-Herzegovina, is 47.14% manganese, and 50.54% MnO from Chikla, India, is 39.14%.
The rhodonite sheet is not one of the 176 in this site's reference set; it was fetched as a comparator for this page and is counted in no survey figure here.
The 1.5-point rule: why hardness decides and the scale does not
Rhodochrosite and rhodonite are separated by 1.5 Mohs points and by nothing you can weigh. Rhodochrosite is hardness 3.5 to 4 and rhodonite 5.5 to 6.5. A steel point that bites easily is consistent with rhodochrosite; one that barely marks or skates is consistent with rhodonite, or with quartz, which is hardness 7. The technique, including why you wipe the mark before deciding, is on how to test mineral hardness properly.
Density is the trap. Rhodochrosite's measured density is 3.70 and rhodonite's 3.57 to 3.76. On a 20.00 g piece that is 14.59 g in water against 14.40 to 14.68 g: rhodochrosite's value falls inside rhodonite's range, so hydrostatic weighing, the method that settles aragonite against calcite, cannot choose here at all.
Cleavage confirms it on a broken edge. Rhodochrosite's {10-11} cleavage is perfect and gives rhombs. Rhodonite has two perfect cleavages at 92.5 degrees, close to square, and a third, good, on {001}. Reading a broken surface is covered on cleavage or fracture. For a gemmologist with a refractometer there is a fourth check: the rhodochrosite sheet prints indices of 1.810 and 1.597, a birefringence of 0.213, and the rhodonite sheet 1.711 to 1.748, a birefringence of 0.013 to 0.014.
How strongly does rhodochrosite bend light? 12th of 138 sheets
Rhodochrosite's birefringence of 0.213 is the 12th widest among the 138 sheets in this site's reference set that print two or more refractive indices. Method: the 176 Handbook sheets were converted with pdftotext -layout, every index value following an equals sign in the optical block was read by regular expression, and the spread taken as the highest printed value minus the lowest, so for sheets that print ranges it is the maximum. Eleven sheets print a wider spread, among them smithsonite at 0.231 and siderite at 0.242; calcite, rhodochrosite's series partner, is 16th at 0.172. Rhodonite, from outside the set, is not counted; at 0.013 to 0.014 it would have 118 of the 138 sheets above it.
Why rhodochrosite and rhodonite share localities, and who each answer is wrong for
The two species grow in the same manganese deposits. The rhodochrosite sheet lists rhodonite as a metamorphic associate, and the two Distribution fields name two of the same places: Cavnic (Kapnik), Romania, and Butte, Silver Bow Co., Montana. Rhodonite's own sheet adds gem crystals at Broken Hill, New South Wales and Morro da Mina, Brazil.
Who the answer rhodonite is wrong for: anyone holding pink rhombs or scalenohedra that a steel point marks; that is rhodochrosite, whatever the label says. Who the answer rhodochrosite is wrong for: anyone holding massive pink material with a black manganese-oxide skin that shrugs off steel. Who neither answer suits: a pink crust on manganese ore that is too thin to test, where the honest label says manganese mineral, untested. The rhodochrosite species page covers crystal habit and the banded material; the identification guides are indexed at the collecting guides. Nothing here is offered for sale; the wanted list is the only commercial route.