Comparison · Minerals vs Quartz Family
Cordierite vs Quartz
Cordierite and Quartz are easy to confuse. Both sit near Mohs 7–7.5, 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 Cordierite and Quartz
- Both sit near Mohs 7–7.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- They overlap in purple, gray, and yellow, but Cordierite also comes in blue and Quartz also comes in clear, pink, black, and brown.
- Well-formed crystals give it away: Cordierite is Orthorhombic, Quartz is Trigonal.
Cordierite vs Quartz properties
| Property | Cordierite | Quartz |
|---|---|---|
| Type | Minerals | Quartz Family |
| Mohs hardness | 7–7.5 | 7 |
| Luster | Vitreous | Vitreous, greasy on fracture surfaces |
| Streak | White | White |
| Transparency | Transparent to translucent | Transparent to translucent |
| Specific gravity | 2.6–2.66 | 2.65 |
| Crystal system | Orthorhombic | Trigonal |
| Common colors | Blue, Violet-blue, Gray, Yellowish gray | 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 Cordierite, and premium Quartz can reach $250 or more.
About Cordierite
Cordierite is a magnesium iron aluminum cyclosilicate, (Mg,Fe)2Al4Si5O18, best known for its strong pleochroism, appearing blue-violet, gray, or pale yellow depending on the angle from which it is viewed. Its transparent gem variety, called iolite, has long been nicknamed 'water sapphire' for its violet-blue color. It crystallizes in the orthorhombic system and typically forms stubby, pseudo-hexagonal crystals.
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.
Cordierite vs Quartz FAQ
Is Cordierite the same as Quartz?
No. Cordierite is a mineral while Quartz is a quartz family. Both sit near Mohs 7–7.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Cordierite from Quartz?
Both sit near Mohs 7–7.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. They overlap in purple, gray, and yellow, but Cordierite also comes in blue and Quartz also comes in clear, pink, black, and brown. Well-formed crystals give it away: Cordierite is Orthorhombic, Quartz is Trigonal.
Which is harder, Cordierite or Quartz?
They are about equally hard, both near Mohs 7–7.5.
Which is more valuable, Cordierite or Quartz?
Quartz is usually the more valuable of the two: a typical collector specimen runs about $35 against $20 for Cordierite, and premium Quartz can reach $250 or more.
