Comparison · Feldspar Group vs Quartz Family
Feldspar vs Quartz
Feldspar and Quartz are easy to confuse. Both sit near Mohs 6–6.5, 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 Feldspar and Quartz
- Both sit near Mohs 6–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- They overlap in pink, gray, and clear, but Feldspar also comes in green and Quartz also comes in purple, yellow, black, and brown.
- Well-formed crystals give it away: Feldspar is Monoclinic to Triclinic (depending on species), Quartz is Trigonal.
Feldspar vs Quartz properties
| Property | Feldspar | Quartz |
|---|---|---|
| Type | Feldspar Group | Quartz Family |
| Mohs hardness | 6–6.5 | 7 |
| Luster | Vitreous to pearly | Vitreous, greasy on fracture surfaces |
| Streak | White | White |
| Transparency | Transparent to translucent | Transparent to translucent |
| Specific gravity | 2.55–2.76 | 2.65 |
| Crystal system | Monoclinic to Triclinic (depending on species) | Trigonal |
| Common colors | White, Pink, Gray, Green (amazonite), Colorless | 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 Feldspar, and premium Quartz can reach $250 or more.
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.
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.
Feldspar vs Quartz FAQ
Is Feldspar the same as Quartz?
No. Feldspar is a feldspar group while Quartz is a quartz family. Both sit near Mohs 6–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Feldspar from Quartz?
Both sit near Mohs 6–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. They overlap in pink, gray, and clear, but Feldspar also comes in green and Quartz also comes in purple, yellow, black, and brown. Well-formed crystals give it away: Feldspar is Monoclinic to Triclinic (depending on species), Quartz is Trigonal.
Which is harder, Feldspar or Quartz?
Quartz is harder: Mohs 7 against Mohs 6–6.5 for Feldspar.
Which is more valuable, Feldspar or Quartz?
Quartz is usually the more valuable of the two: a typical collector specimen runs about $35 against $20 for Feldspar, and premium Quartz can reach $250 or more.
