Comparison · Minerals vs Feldspar Group
Andalusite vs Feldspar
Andalusite and Feldspar are easy to confuse. Both sit near Mohs 6.5–7.5, 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 Andalusite and Feldspar
- Both sit near Mohs 6.5–7.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Andalusite feels noticeably heavier for its size (specific gravity 3.13–3.21 versus 2.55–2.76 for Feldspar).
- They overlap in green, gray, and pink, but Andalusite also comes in brown and red and Feldspar also comes in clear.
- Well-formed crystals give it away: Andalusite is Orthorhombic, Feldspar is Monoclinic to Triclinic (depending on species).
Andalusite vs Feldspar properties
| Property | Andalusite | Feldspar |
|---|---|---|
| Type | Minerals | Feldspar Group |
| Mohs hardness | 6.5–7.5 | 6–6.5 |
| Luster | Vitreous | Vitreous to pearly |
| Streak | White | White |
| Transparency | Transparent to translucent | Transparent to translucent |
| Specific gravity | 3.13–3.21 | 2.55–2.76 |
| Crystal system | Orthorhombic | Monoclinic to Triclinic (depending on species) |
| Common colors | Reddish brown, Olive green, Gray, Pink | White, Pink, Gray, Green (amazonite), Colorless |
| Rarity | common | common |
| Typical specimen value | $2–$150+ | $2–$150+ |
Which is more valuable?
Typical specimens of Andalusite and Feldspar trade in a similar range, around $20.
About Andalusite
Andalusite is an aluminum silicate, Al2SiO5, and one of three natural polymorphs sharing that exact formula along with kyanite and sillimanite. It crystallizes in the orthorhombic system as stout, nearly square prisms formed under low-pressure, moderate-temperature metamorphism. Its variety chiastolite, which displays a dark cross pattern in cross-section, makes it one of the more recognizable metamorphic minerals to casual collectors.
About Feldspar
Feldspar is not a single mineral but a group of related aluminosilicate minerals, comprising the potassium feldspars, orthoclase, microcline, and sanidine, and the plagioclase series running from albite to anorthite, together making up roughly 60 percent of Earth's crust by volume. All share a similar framework silicate structure, two cleavage directions near 90 degrees, and moderate hardness, but differ in composition, color, and crystal system. As the most abundant mineral group on the planet, feldspar defines granite, basalt, gneiss, and countless other rock types.
Andalusite vs Feldspar FAQ
Is Andalusite the same as Feldspar?
No. Andalusite is a mineral while Feldspar is a feldspar group. Both sit near Mohs 6.5–7.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Andalusite from Feldspar?
Both sit near Mohs 6.5–7.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Andalusite feels noticeably heavier for its size (specific gravity 3.13–3.21 versus 2.55–2.76 for Feldspar). They overlap in green, gray, and pink, but Andalusite also comes in brown and red and Feldspar also comes in clear.
Which is harder, Andalusite or Feldspar?
Andalusite is harder: Mohs 6.5–7.5 against Mohs 6–6.5 for Feldspar.
Which is more valuable, Andalusite or Feldspar?
Typical specimens of Andalusite and Feldspar trade in a similar range, around $20.
