Trachyte: Identification, Properties & Value

Trachyte properties at a glance

Type	Igneous Rocks
Chemical formula	Alkali feldspar-rich volcanic rock
Mohs hardness	6
Luster	dull
Streak	Light gray to white
Cleavage	None to variable by phenocrysts
Fracture	Uneven to conchoidal
Specific gravity	2.6
Transparency	opaque
Common colors	Light gray, Tan, Pink, Brown, Greenish gray, White
Rarity	common

Geology & background

Forms when alkali feldspar-rich lava cools at or near the surface, often producing fine-grained or porphyritic volcanic texture.

Trachyte helps geologists identify alkali-rich volcanic rocks and volcanic equivalents of syenitic magmas.

How to identify Trachyte

Look for light gray, tan, pinkish, or brown fine-grained volcanic texture.
Feldspar phenocrysts can support trachyte when visible.
Trachyte generally looks lighter and more feldspar-rich than basalt.
It can overlap visually with rhyolite or andesite, so context helps.

Where Trachyte is found

Reported from multiple igneous terrains worldwide; verify locality against specimen provenance when available.

How much is Trachyte worth?

Entry-level specimen	$1
Typical collector specimen	$10
Premium specimen	$75+

Trachyte is usually valued for teaching, field context, locality, texture, color, mineral content, or unusually attractive specimens rather than high gem value.

Common uses

Field identification
Volcanic rock comparison
Education
Building stone in some regions

Interesting facts

Trachyte is the volcanic counterpart of syenite.
Its name refers to a rough texture seen in some specimens.
Porphyritic trachyte can contain visible feldspar crystals in a fine groundmass.