Comparison · Minerals vs Quartz Family
Franklinite vs Quartz
Franklinite and Quartz are easy to confuse. Quartz is harder (Mohs 7) than Franklinite (Mohs 5.5–6.5), so Quartz will scratch Franklinite and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Franklinite and Quartz
- Quartz is harder (Mohs 7) than Franklinite (Mohs 5.5–6.5), so Quartz will scratch Franklinite and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will.
- Streak color differs: Franklinite leaves a reddish brown to black streak on unglazed porcelain, Quartz leaves white.
- Luster is different: Franklinite is metallic to submetallic while Quartz is vitreous, greasy on fracture surfaces.
- Franklinite feels noticeably heavier for its size (specific gravity 5.1–5.2 versus 2.65 for Quartz).
- Hold a thin edge to the light: Franklinite is Opaque, Quartz is Transparent to translucent.
- They overlap in black and brown, but Quartz also comes in clear, purple, yellow, pink, and gray.
- Well-formed crystals give it away: Franklinite is Isometric, Quartz is Trigonal.
Franklinite vs Quartz properties
| Property | Franklinite | Quartz |
|---|---|---|
| Type | Minerals | Quartz Family |
| Mohs hardness | 5.5–6.5 | 7 |
| Luster | Metallic to submetallic | Vitreous, greasy on fracture surfaces |
| Streak | Reddish brown to black | White |
| Transparency | Opaque | Transparent to translucent |
| Specific gravity | 5.1–5.2 | 2.65 |
| Crystal system | Isometric | Trigonal |
| Common colors | Black, Brownish black | Colorless, White, Purple (amethyst), Yellow (citrine), Pink (rose), Brown/black (smoky) |
| Rarity | common | common |
| Typical specimen value | $2–$150+ | $5–$250+ |
Which is more valuable?
Quartz is usually the more valuable of the two: a typical collector specimen runs about $35 against $20 for Franklinite, and premium Quartz can reach $250 or more.
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 Quartz
Quartz is silicon dioxide, SiO2, one of the most abundant minerals in Earth's continental crust, crystallizing in the trigonal division of the hexagonal crystal system with a hardness of 7 that makes it a standard reference point on the Mohs scale. Its six-sided prismatic crystals, often terminated by pyramidal points, are among the most recognizable crystal shapes in mineralogy. Quartz occurs in nearly every rock type and geologic setting, from granite pegmatites to sedimentary sandstones to hydrothermal veins.
Franklinite vs Quartz FAQ
Is Franklinite the same as Quartz?
No. Franklinite is a mineral while Quartz is a quartz family. Quartz is harder (Mohs 7) than Franklinite (Mohs 5.5–6.5), so Quartz will scratch Franklinite and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will.
How can you tell Franklinite from Quartz?
Quartz is harder (Mohs 7) than Franklinite (Mohs 5.5–6.5), so Quartz will scratch Franklinite and not the other way round. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will. Streak color differs: Franklinite leaves a reddish brown to black streak on unglazed porcelain, Quartz leaves white. Luster is different: Franklinite is metallic to submetallic while Quartz is vitreous, greasy on fracture surfaces.
Which is harder, Franklinite or Quartz?
Quartz is harder: Mohs 7 against Mohs 5.5–6.5 for Franklinite.
Which is more valuable, Franklinite or Quartz?
Quartz is usually the more valuable of the two: a typical collector specimen runs about $35 against $20 for Franklinite, and premium Quartz can reach $250 or more.
