Is rhodochrosite magnetic
Not strongly. Its sheet records no magnetism; USGS pulled rhodochrosite at 0.10 to 0.60 amp, paramagnetic, where magnetite took 0.01 and quartz was not pulled.
Is rhodochrosite magnetic? Not in the sense magnetite is. Its Handbook sheet, MnCO3, hardness 3.5 to 4, records no magnetic property. USGS Open-File Report 99-529 extracted it on a laboratory separator at 0.10 to 0.60 amp, its paramagnetic range, where magnetite came out at 0.01 amp. Manganese, USGS says, raises carbonate susceptibility.
In short
- The reference sheet is silent. The Handbook of Mineralogy sheet for rhodochrosite records hardness, density, cleavage and optics and no magnetic property. None of the five calcite-group sheets in this site's 176-sheet reference set mentions magnetism at all.
- A measurement exists, from USGS. Rosenblum and Brownfield ran 5 rhodochrosite samples, 125 to 150 µm grains, through a Frantz isodynamic separator at a 15 degree side tilt. They came out at 0.10 to 0.60 amp, best 0.20 to 0.40.
- The 1.70-amp line. USGS calls a mineral paramagnetic if the separator pulls it at up to 1.70 amp, its maximum, and diamagnetic if it does not. Rhodochrosite is paramagnetic on that definition. Ferromagnetic minerals, strongly attracted to a magnet, are a separate class: magnetite's best range was 0.01 amp, a twentieth to a fortieth of the current rhodochrosite needed.
- Manganese is the reason USGS gives. Its conclusions name manganese carbonate (rhodochrosite) as more magnetic than the other carbonates. Calcite was not pulled at 1.70 amp; manganese-bearing calcite came out at 0.50 to 1.70. Rhodochrosite is 47.79% manganese by mass, calculated.
- What this does not tell you. Neither source tests a hand magnet, so this page does not predict what one will do. A strong pull on a specimen points to another mineral in it; the method for finding it is on the tetrahedrite magnet page.
| Mineral | Formula (Handbook) | Magnetism on the Handbook sheet | USGS total range (amp) | USGS best range (amp) | Samples | Class, by USGS definitions |
|---|---|---|---|---|---|---|
| Rhodochrosite | MnCO3 | None recorded | 0.10 to 0.60 | 0.20 to 0.40 | 5 | Paramagnetic |
| Siderite | FeCO3 | None recorded | 0.10 to 0.50 | 0.20 to 0.30 | 17 | Paramagnetic |
| Calcite, manganese-bearing | Listed by USGS as Calcite-(Mn); no separate Handbook sheet | Not applicable | 0.50 to 1.70 | 0.90 to 1.10 | 1 | Paramagnetic |
| Calcite | CaCO3 | None recorded | Above 1.70 | Above 1.70 | 8 | Diamagnetic |
| Magnesite | MgCO3 | None recorded | Above 1.70 | Above 1.70 | 2 | Diamagnetic |
| Smithsonite | ZnCO3 | None recorded | Above 1.70 | Above 1.70 | 3 | Diamagnetic |
| Rhodonite (sheet outside the 176) | (Mn2+,Fe2+,Mg,Ca)SiO3 | None recorded | 0.05 to 0.70 | 0.20 to 0.30 | 4 | Paramagnetic |
| Quartz | SiO2 | None recorded | Above 1.70 | Above 1.70 | 10 | Diamagnetic (often locked with other species) |
| Magnetite | Fe3O4 | Strongly magnetic | Below 0.01 to 0.05 | 0.01 | 6 | Ferromagnetic |
Is rhodochrosite magnetic? What the reference sheet records
The Handbook of Mineralogy sheet for rhodochrosite records no magnetic property. It gives Mn2+CO3, hexagonal, calcite group, perfect rhombohedral cleavage, hardness 3.5 to 4, measured density 3.70, and colours from pink, rose-red and cherry-red to yellowish gray and cinnamon-brown. It records no fluorescence either.
Method. All five sheets in this site's 176-sheet reference set whose Mineral Group line reads calcite group, calcite, magnesite, rhodochrosite, siderite and smithsonite, were searched case-insensitively for the string magnet. None contains it. Silence in a reference sheet is absence from the source, not a measured zero, which is why the next section goes to a measurement. The species is on rhodochrosite.
Manganese by mass, worked. With standard atomic weights, Mn 54.938, C 12.011, O 15.999, MnCO3 has a formula mass of 114.946, of which manganese is 47.79%. The same weights give 61.71% MnO, which is the figure in the sheet's ideal-composition column, so the formula and the arithmetic agree.
What the USGS separator measured, and the 1.70-amp line
USGS measured rhodochrosite's response on a laboratory magnetic separator, and it falls in the paramagnetic range. USGS Open-File Report 99-529, Magnetic Susceptibilities of Minerals (Rosenblum and Brownfield) passes dry grains, 125 to 150 µm, down a chute through an electromagnet at a 15 degree side tilt, raising the current in 0.10 amp steps. Rhodochrosite, 5 samples, was extracted at 0.10 to 0.60 amp, most of it at 0.20 to 0.40.
The 1.70-amp line, in USGS's own definitions. Ferromagnetic refers to minerals strongly attracted to a magnet, like a piece of iron, and the report names magnetite, maghemite, pyrrhotite and pentlandite. Paramagnetic refers to minerals less magnetic than that, separable at up to 1.70 amp, the separator's maximum. Diamagnetic minerals are not pulled at 1.70 amp. Rhodochrosite, pulled from 0.10 amp, is paramagnetic on that scale; calcite, magnesite, smithsonite and quartz are diamagnetic; magnetite's best range was 0.01 amp.
Worked comparison. Rhodochrosite's best range, 0.20 to 0.40 amp, is 20 to 40 times magnetite's 0.01 amp. That is a ratio of separator currents, not of susceptibilities, which the report says it does not measure in cgs units; it is enough to place rhodochrosite far from magnetite on the report's own scale.
Why manganese makes a carbonate more magnetic, per USGS
USGS names manganese as a cause. The report says that, other than iron, only manganese and copper have been noted to bring minerals into the paramagnetic range, and cites manganite, rhodochrosite and rhodonite for manganese. Its conclusions add that, in the carbonate family, manganese carbonate (rhodochrosite) is more magnetic than other species, as iron-bearing carbonates are.
The calcite rows show it inside one species. Calcite, 8 samples, was not pulled at 1.70 amp. A single manganese-bearing calcite came out at 0.50 to 1.70 amp, best 0.90 to 1.10. Calcite and rhodochrosite form a series on the Handbook sheets, and siderite, iron carbonate, ran close to rhodochrosite at 0.10 to 0.50 amp.
Rhodonite will not separate from rhodochrosite this way. Its USGS best range, 0.20 to 0.30 amp, sits inside rhodochrosite's. Hardness does that job, set out on is rhodochrosite the same as rhodonite.
My rhodochrosite pulls a magnet: what that means
A clear pull on a rhodochrosite specimen is information about something else in it. The sheet records nothing, and USGS places the species in a range where a laboratory electromagnet is needed. The sheet's hydrothermal associates include siderite, pyrite and tetrahedrite, and its metamorphic ones hausmannite and alabandite; none of this predicts a hand-magnet result, and we make no prediction.
Localise the pull, then test the grain. That sequence is set out on is tetrahedrite magnetic and applies unchanged; which species in this site's reference set record a magnetic property is on which minerals are magnetic. Neither is repeated here.
Is rhodochrosite a quartz? No: it is a carbonate, hardness 3.5 to 4, where quartz is SiO2, hardness 7, and USGS records quartz as diamagnetic. The identification guides are indexed at the collecting guides. Nothing on this site is offered for sale; the wanted list is the only commercial route.