Comparison · Igneous Rocks
Basalt vs Tephrite
Basalt and Tephrite are easy to confuse because both are igneous rocks. Both sit near Mohs 6, 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 Basalt and Tephrite
- Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Streak color differs: Basalt leaves a variable; test individual minerals streak on unglazed porcelain, Tephrite leaves gray to dark gray.
- They overlap in black, gray, and green, but Tephrite also comes in brown.
Basalt vs Tephrite properties
| Property | Basalt | Tephrite |
|---|---|---|
| Type | Igneous Rocks | Igneous Rocks |
| Mohs hardness | 6 | 6 |
| Luster | dull | dull |
| Streak | Variable; test individual minerals | Gray to dark gray |
| Transparency | opaque | opaque |
| Specific gravity | 3 | 2.85 |
| Crystal system | varies | varies |
| Common colors | Black, Dark Gray, Dark Green | Dark gray, Black, Brown, Gray, Greenish black |
| Rarity | common | uncommon |
| Typical specimen value | $1–$30+ | $1–$75+ |
Which is more valuable?
Tephrite is usually the more valuable of the two: a typical collector specimen runs about $10 against $5 for Basalt, and premium Tephrite can reach $75 or more.
About Basalt
Basalt is a dark, fine-grained volcanic rock that makes up most of the ocean floor and Hawaiian Islands. It often forms distinctive columnar jointing.
About Tephrite
Tephrite is a dark, fine-grained volcanic rock that contains feldspathoid minerals such as nepheline or leucite. It can resemble basalt in hand sample.
Basalt vs Tephrite FAQ
Is Basalt the same as Tephrite?
No. Both are igneous rocks, but they are distinct rock types with different hardness, streak or luster. Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Basalt from Tephrite?
Both sit near Mohs 6, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Streak color differs: Basalt leaves a variable; test individual minerals streak on unglazed porcelain, Tephrite leaves gray to dark gray. They overlap in black, gray, and green, but Tephrite also comes in brown.
Which is harder, Basalt or Tephrite?
They are about equally hard, both near Mohs 6.
Which is more valuable, Basalt or Tephrite?
Tephrite is usually the more valuable of the two: a typical collector specimen runs about $10 against $5 for Basalt, and premium Tephrite can reach $75 or more.
