Comparison · Quartz Family vs Carbonates
Quartz vs Siderite
Quartz and Siderite are easy to confuse. Quartz is harder (Mohs 7) than Siderite (Mohs 4), so Quartz will scratch Siderite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Quartz and Siderite
- Quartz is harder (Mohs 7) than Siderite (Mohs 4), so Quartz will scratch Siderite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
- Siderite feels noticeably heavier for its size (specific gravity 3.96 versus 2.65 for Quartz).
- Hold a thin edge to the light: Quartz is Transparent to translucent, Siderite is translucent.
- They overlap in yellow, gray, and brown, but Quartz also comes in clear, purple, pink, and black.
- Well-formed crystals give it away: Quartz is Trigonal, Siderite is trigonal.
Quartz vs Siderite properties
| Property | Quartz | Siderite |
|---|---|---|
| Type | Quartz Family | Carbonates |
| Mohs hardness | 7 | 4 |
| Luster | Vitreous, greasy on fracture surfaces | vitreous |
| Streak | White | White |
| Transparency | Transparent to translucent | translucent |
| Specific gravity | 2.65 | 3.96 |
| Crystal system | Trigonal | trigonal |
| Common colors | Colorless, White, Purple (amethyst), Yellow (citrine), Pink (rose), Brown/black (smoky) | Yellowish brown, Brown, Tan, Gray |
| Rarity | common | common |
| Typical specimen value | $5–$250+ | $5–$350+ |
Which is more valuable?
Siderite is usually the more valuable of the two: a typical collector specimen runs about $45 against $35 for Quartz, and premium Siderite can reach $350 or more.
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.
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.
Quartz vs Siderite FAQ
Is Quartz the same as Siderite?
No. Quartz is a quartz family while Siderite is a carbonate. Quartz is harder (Mohs 7) than Siderite (Mohs 4), so Quartz will scratch Siderite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
How can you tell Quartz from Siderite?
Quartz is harder (Mohs 7) than Siderite (Mohs 4), so Quartz will scratch Siderite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Siderite feels noticeably heavier for its size (specific gravity 3.96 versus 2.65 for Quartz). Hold a thin edge to the light: Quartz is Transparent to translucent, Siderite is translucent.
Which is harder, Quartz or Siderite?
Quartz is harder: Mohs 7 against Mohs 4 for Siderite.
Which is more valuable, Quartz or Siderite?
Siderite is usually the more valuable of the two: a typical collector specimen runs about $45 against $35 for Quartz, and premium Siderite can reach $350 or more.
