Comparison · Carbonates
Magnesite vs Siderite
Magnesite and Siderite are easy to confuse because both are carbonates. Both sit near Mohs 4, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Magnesite and Siderite
- Both sit near Mohs 4, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Siderite feels noticeably heavier for its size (specific gravity 3.96 versus 3 for Magnesite).
- They overlap in gray, yellow, and brown, but Magnesite also comes in clear.
Magnesite vs Siderite properties
| Property | Magnesite | Siderite |
|---|---|---|
| Type | Carbonates | Carbonates |
| Mohs hardness | 4 | 4 |
| Luster | vitreous | vitreous |
| Streak | White | White |
| Transparency | translucent | translucent |
| Specific gravity | 3 | 3.96 |
| Crystal system | trigonal | trigonal |
| Common colors | White, Gray, Yellowish, Brown, Colorless | Yellowish brown, Brown, Tan, Gray |
| Rarity | common | common |
| Typical specimen value | $3–$150+ | $5–$350+ |
Which is more valuable?
Siderite is usually the more valuable of the two: a typical collector specimen runs about $45 against $25 for Magnesite, and premium Siderite can reach $350 or more.
About Magnesite
Magnesite is a magnesium carbonate mineral that forms white to gray crystalline masses and, less commonly, rhombohedral crystals. It is an important source of magnesium and refractory magnesia.
About Siderite
Siderite is an iron carbonate mineral that occurs as honey-brown to tan rhombohedral crystals, often with curved or saddle-shaped faces. It also forms massive and concretionary masses and is a recognized iron ore.
Magnesite vs Siderite FAQ
Is Magnesite the same as Siderite?
No. Both are carbonates, but they are distinct species with different hardness, streak or luster. Both sit near Mohs 4, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Magnesite from Siderite?
Both sit near Mohs 4, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Siderite feels noticeably heavier for its size (specific gravity 3.96 versus 3 for Magnesite). They overlap in gray, yellow, and brown, but Magnesite also comes in clear.
Which is harder, Magnesite or Siderite?
They are about equally hard, both near Mohs 4.
Which is more valuable, Magnesite or Siderite?
Siderite is usually the more valuable of the two: a typical collector specimen runs about $45 against $25 for Magnesite, and premium Siderite can reach $350 or more.
