Rhyolite | Gemopedia

Rhyolite is a volcanic rock similar in its chemistry to granite. Most rhyolites are porphyritic, with larger crystals in a fine-grained matrix of crystals too small to been seen with the naked eye. Rhyolite is silica-rich, giving it a light range of color, often found with banding throughout. This beautiful stone is often used in ornamentation.
Alternate
Names
Hickoryite, Rainbow Hickoryite, Spiderweb Rhyolite, Birds Eye Rhyolite, Mushroom Rhyolite, Wonderstone
Colors
Beige, Brown, Red, Orange, Green, White To Gray

Rhyolite Classification

Common Name

Rhyolite

Species

Rhyolite

Variety

Colors

Beige, Brown, Red, Orange, Green, White To Gray

Alternate Names

Hickoryite, Rainbow Hickoryite, Spiderweb Rhyolite, Birds Eye Rhyolite, Mushroom Rhyolite, Wonderstone

Gemstone Groups

Key Separations

Comments

Rhyolite is a extrusive igneous rock composed of mostly quartz and feldspar and is often mistaken for jasper. Hickoryite is a banded version of rhyolite. Rainbow hickoryite is a muti-color banded form of rhyolite. Misnomers: butterfly jasper, rain forest jasper, solar flare jasper, Nevada paint jasper, lily pad jasper, leopard jasper, mushroom jasper and Mexican poppy jasper

Rhyolite Optical Properties

Transparency

Opaque

Refractive Index

Birefringence

Optic Character

NA

Optic Sign

NA

Polariscope Reaction

Fluorescence

SWUV:
LWUV:

CCF Reaction

Pleochroism

None

Dispersion

Comments

Rhyolite Chemistry & Crystallography

Chemical Name

silicon dioxide + potassium Oxide

Chemical Formula

SiO2+K2O

Synthesis

Crystal System

NA

Classification

Rock

Nature

Natural

Crystallinity

Aggregate

Comments

Rhyolite Characteristic Physical Properties

Hardness

6.5-7

Streak

Specific Gravity

Toughness

Inclusions

Rhyolite might show banding or spherical growth. If stones are viewed in cross-section using magnification they typically show crystalline growth and may show radiating needle patterns.

Luster

Stability

Fracture

Cleavage

None

Comments

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