Comparison · Feldspar Group vs Igneous Rocks
Feldspar vs Porphyry
Feldspar and Porphyry 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 Porphyry
- Both sit near Mohs 6–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Hold a thin edge to the light: Feldspar is Transparent to translucent, Porphyry is Opaque.
- They overlap in gray and green, but Feldspar also comes in pink and clear and Porphyry also comes in purple and red.
Feldspar vs Porphyry properties
| Property | Feldspar | Porphyry |
|---|---|---|
| Type | Feldspar Group | Igneous Rocks |
| Mohs hardness | 6–6.5 | 5–7 |
| Luster | Vitreous to pearly | Dull to vitreous |
| Streak | White | — |
| Transparency | Transparent to translucent | Opaque |
| Specific gravity | 2.55–2.76 | 2.6–2.8 |
| Crystal system | Monoclinic to Triclinic (depending on species) | — |
| Common colors | White, Pink, Gray, Green (amazonite), Colorless | Purple, Red, Gray, Green |
| Rarity | common | common |
| Typical specimen value | $2–$150+ | $1–$75+ |
Which is more valuable?
Feldspar is usually the more valuable of the two: a typical collector specimen runs about $20 against $10 for Porphyry, and premium Feldspar can reach $150 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 Porphyry
Porphyry is a textural term for any igneous rock that contains large, visible crystals called phenocrysts embedded in a much finer-grained groundmass, rather than a description of a specific mineral composition. The texture records a two-stage cooling history, slow crystal growth at depth followed by rapid cooling near or at the surface. Porphyry can be volcanic or shallow intrusive and of almost any composition, from basaltic to rhyolitic.
Feldspar vs Porphyry FAQ
Is Feldspar the same as Porphyry?
No. Feldspar is a feldspar group while Porphyry is a igneous rock. 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 Porphyry?
Both sit near Mohs 6–6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Hold a thin edge to the light: Feldspar is Transparent to translucent, Porphyry is Opaque. They overlap in gray and green, but Feldspar also comes in pink and clear and Porphyry also comes in purple and red.
Which is harder, Feldspar or Porphyry?
They are about equally hard, both near Mohs 6–6.5.
Which is more valuable, Feldspar or Porphyry?
Feldspar is usually the more valuable of the two: a typical collector specimen runs about $20 against $10 for Porphyry, and premium Feldspar can reach $150 or more.
