Comparison · Minerals
Franklinite vs Magnetite
Franklinite and Magnetite are easy to confuse because both are minerals. Both sit near Mohs 5.5–6.5, 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 Franklinite and Magnetite
- Both sit near Mohs 5.5–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Streak color differs: Franklinite leaves a reddish brown to black streak on unglazed porcelain, Magnetite leaves black.
- Both look metallic, so compare color, tarnish and weight rather than shine.
- They overlap in black, but Franklinite also comes in brown and Magnetite also comes in gray.
- Well-formed crystals give it away: Franklinite is Isometric, Magnetite is Cubic.
Franklinite vs Magnetite properties
| Property | Franklinite | Magnetite |
|---|---|---|
| Type | Minerals | Minerals |
| Mohs hardness | 5.5–6.5 | 5.5–6.5 |
| Luster | Metallic to submetallic | Metallic to submetallic/dull |
| Streak | Reddish brown to black | Black |
| Transparency | Opaque | Opaque |
| Specific gravity | 5.1–5.2 | 5.17–5.2 |
| Crystal system | Isometric | Cubic |
| Common colors | Black, Brownish black | Black, Iron-black, Gray-black |
| Rarity | common | common |
| Typical specimen value | $2–$150+ | $2–$150+ |
Which is more valuable?
Typical specimens of Franklinite and Magnetite trade in a similar range, around $20.
About Franklinite
Franklinite is a zinc iron manganese oxide, (Zn,Mn,Fe)(Fe,Mn)2O4, belonging to the spinel group and crystallizing in the isometric system, usually as black octahedral crystals or granular masses. It is virtually unique to the zinc deposits of Franklin and Sterling Hill, New Jersey, where it occurs in an assemblage found almost nowhere else on Earth. Though weakly magnetic, it is chemically distinct from true magnetite.
About Magnetite
Magnetite is an iron oxide mineral, Fe3O4, crystallizing in the cubic system and the most strongly magnetic naturally occurring mineral on Earth, capable of attracting steel objects and even acting as a natural compass in its lodestone form. It forms in a remarkably wide range of igneous, metamorphic, and sedimentary environments, making it one of the most common accessory minerals in rock-forming systems worldwide. Ancient sailors and travelers used naturally magnetized lodestone, a variety of magnetite, as the earliest known compasses.
Franklinite vs Magnetite FAQ
Is Franklinite the same as Magnetite?
No. Both are minerals, but they are distinct species with different hardness, streak or luster. Both sit near Mohs 5.5–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Franklinite from Magnetite?
Both sit near Mohs 5.5–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Streak color differs: Franklinite leaves a reddish brown to black streak on unglazed porcelain, Magnetite leaves black. Both look metallic, so compare color, tarnish and weight rather than shine.
Which is harder, Franklinite or Magnetite?
They are about equally hard, both near Mohs 5.5–6.5.
Which is more valuable, Franklinite or Magnetite?
Typical specimens of Franklinite and Magnetite trade in a similar range, around $20.
