Gemstone profile and identification guide

Mahogany Obsidian

Mahogany obsidian is an obsidian variety showing reddish-brown mottling from iron-rich inclusions.

5.5 Mohs Brown, Black Volcanic Glass (Obsidian Variety)

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Overview

Mahogany obsidian is an obsidian variety showing reddish-brown mottling from iron-rich inclusions.

Did you know? Despite moderate hardness, obsidian can be brittle because it is natural glass.

Use this profile as a collector reference and educational guide for quick on-page comparison, then validate with the interactive identification system.

Identification

Name: Mahogany Obsidian

Scientific classification: Volcanic Glass (Obsidian Variety)

Hardness: 5.5 Mohs

Transparency: opaque

Lustre: vitreous

Crystal system: Amorphous

Primary colour: Brown

Secondary colour: Black

Colour family: Browns

Glassy luster, conchoidal fracture, and brown-black mottling are core identifiers.

Verification Status

Status: verified-core-fields

Reference priority: GIA, Gem-A, Mindat, International Gem Society

Core identity, locality, and physical-property fields reviewed against standard gemological references.

Trade-name entries include conservative composition/treatment disclosures where needed.

Physical Properties

Hardness category: medium

Hardness value: 5.5 Mohs

Chemical composition: Natural silica-rich volcanic glass with iron oxide coloration

Crystal system: Amorphous

Common locations: United States, Mexico, Armenia, Turkey

Learn more: Gem-A gemstone education resources.

Colour Variations

Reddish-brown and black mottled volcanic glass.

Optical effects: Mottled Color Pattern

Detailed Gemology

Mineral species: Obsidian (mahogany variety)

Mineral group: Volcanic glass mineraloid

Chemical formula: Natural silica-rich volcanic glass with iron oxide coloration

Mohs hardness: 5.5

Crystal system: Amorphous

Lustre: vitreous

Transparency: opaque

Streak: White

Cleavage: None

Fracture: Conchoidal

Specific gravity: 2.35-2.60

Refractive index: Approximately 1.48-1.51

Optical phenomena: Patterned mottling

Colour range: Brown-red and black mottled

Common inclusions: Flow bands, bubbles, iron-rich zones

Geological environment: Extrusive volcanic rhyolitic lava flows

Principal mining regions: United States, Mexico, Armenia, Turkey

Important commercial sources: Mahogany obsidian is sourced from volcanic glass localities with iron-rich flow textures

Historical significance: Long-used ornamental and tool stone in many cultures.

Common treatments: Usually untreated.

Synthetic or imitation forms: Colored glass can imitate appearance.

Common look-alikes: Dark jasper, glass, slag-like materials

Jewellery uses: Mahogany Obsidian is used chiefly for Decorative pieces emphasizing natural mottled patterns.. In the trade it is commonly fashioned as cabochons, beads, carvings, and polished ornamental pieces, with Mohs hardness 5.5 guiding suitable jewellery applications.

Care recommendations: Can chip due to glassy conchoidal fracture; avoid impact and edge abrasion.

Cross-check profile data with GIA Gem Encyclopedia and Mindat entry for Mahogany Obsidian.

Formation

Forms by rapid cooling of silica-rich lava, preserving glassy structure and colour zoning.

Origin

Mahogany obsidian is sourced from volcanic glass localities with iron-rich flow textures

Uses

Best for: Mahogany Obsidian is used chiefly for Decorative pieces emphasizing natural mottled patterns.. In the trade it is commonly fashioned as cabochons, beads, carvings, and polished ornamental pieces, with Mohs hardness 5.5 guiding suitable jewellery applications.

Ideal uses: Decorative pieces emphasizing natural mottled patterns.

Care

Can chip due to glassy conchoidal fracture; avoid impact and edge abrasion.

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