Comparison · Minerals
Andradite vs Goethite
Andradite and Goethite are easy to confuse because both are minerals. Andradite is harder (Mohs 6.5–7) than Goethite (Mohs 5–5.5), so Andradite will scratch Goethite 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 Andradite and Goethite
- Andradite is harder (Mohs 6.5–7) than Goethite (Mohs 5–5.5), so Andradite will scratch Goethite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
- Streak color differs: Andradite leaves a white streak on unglazed porcelain, Goethite leaves yellowish brown.
- Hold a thin edge to the light: Andradite is Transparent to translucent, Goethite is Opaque, translucent in thin splinters.
- They overlap in yellow, brown, and black, but Andradite also comes in green and Goethite also comes in red.
- Well-formed crystals give it away: Andradite is Cubic, Goethite is Orthorhombic.
Andradite vs Goethite properties
| Property | Andradite | Goethite |
|---|---|---|
| Type | Minerals | Minerals |
| Mohs hardness | 6.5–7 | 5–5.5 |
| Luster | Vitreous to resinous/adamantine | Adamantine to dull/earthy, silky |
| Streak | White | Yellowish brown |
| Transparency | Transparent to translucent | Opaque, translucent in thin splinters |
| Specific gravity | 3.8–3.9 | 3.3–4.3 |
| Crystal system | Cubic | Orthorhombic |
| Common colors | Yellow-green (demantoid), Brown, Black (melanite), Yellow | Brown, Yellowish brown, Reddish brown, Black |
| Rarity | common | common |
| Typical specimen value | $2–$150+ | $2–$150+ |
Which is more valuable?
Typical specimens of Andradite and Goethite trade in a similar range, around $20.
About Andradite
Andradite is a calcium-iron garnet, Ca3Fe2(SiO4)3, one of six species making up the isomorphous garnet group. It occurs in shades of yellow-green, brown, and black depending on trace elements, and includes the gem varieties demantoid, colored green by chromium, and topazolite, a golden-yellow form. Its isometric habit and high refractive index give faceted stones exceptional fire, occasionally surpassing that of diamond.
About Goethite
Goethite is an iron oxide-hydroxide, FeO(OH), and one of the most common iron-bearing minerals, formed by the weathering of other iron minerals such as pyrite, magnetite, and siderite. It crystallizes in the orthorhombic system but rarely shows well-formed crystals, instead forming botryoidal, stalactitic, or earthy masses. Named for the German writer and naturalist Johann Wolfgang von Goethe, it is a major constituent of the mineral mixture commonly called limonite.
Andradite vs Goethite FAQ
Is Andradite the same as Goethite?
No. Both are minerals, but they are distinct species with different hardness, streak or luster. Andradite is harder (Mohs 6.5–7) than Goethite (Mohs 5–5.5), so Andradite will scratch Goethite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not.
How can you tell Andradite from Goethite?
Andradite is harder (Mohs 6.5–7) than Goethite (Mohs 5–5.5), so Andradite will scratch Goethite and not the other way round. A steel knife blade (Mohs 5.5) scratches it; a copper coin does not. Streak color differs: Andradite leaves a white streak on unglazed porcelain, Goethite leaves yellowish brown. Hold a thin edge to the light: Andradite is Transparent to translucent, Goethite is Opaque, translucent in thin splinters.
Which is harder, Andradite or Goethite?
Andradite is harder: Mohs 6.5–7 against Mohs 5–5.5 for Goethite.
Which is more valuable, Andradite or Goethite?
Typical specimens of Andradite and Goethite trade in a similar range, around $20.
