Obsidian

Object/Artifact

-

Crater Rock Museum

Obsidian sphere

Obsidian sphere

Name/Title

Obsidian

Entry/Object ID

2014.1.154

Description

Chemical Composition: SiO2 Description: Common name: Obsidian Chemistry: SiO2 Class: Mineraloids Location: Unknown Description: A sphere that sits on a ceramic ring base. It is a glossy black color. PHYSICAL CHARACTERISTICS: Color is dark green to dark brown and black, also can show sheens of gold or green, yellow, blue and/or purple coloration. Sometimes with white inclusions (Snowflake Obsidian). Luster is vitreous. Transparency: Obsidian is translucent in any stone of appreciable size. Crystal System does not apply because obsidian is amorphous. Habits include compact nodules or as massive layers between other volcanic rocks Fracture is conchoidal. Hardness is 5 - 5.5 (much softer than quartz). Specific Gravity is approximately 2.6 (average) Streak is white. Best Field Indicators are color, fracture, flow bubbles, softness, association with other volcanic rocks and lack of crystal faces.. Fracture: Conchoidal Hardness: 5 Apatite Luster: Vitreous Occurrence: Notable Occurrences include Italy; Mexico; Scotland; Arizona, Colorado, Texas, Utah and Idaho, USA, as well as the Cascade Volcanic Mountain range and its associated lava beds, which stretches from Northern California into Washington state. Rock Type: Igneous Specific Gravity: 2.6 Streak: White Variety: Obsidian has several varieties. Obsidian can contain small bubbles of air that are aligned along layers created as the molten rock was flowing just before being cooled. These bubbles can produce interesting effects such as a golden sheen, known as Sheen Obsidian or a rainbow sheen called Rainbow Obsidian. Inclusions of small, white, radially clustered crystals of cristobalite in the black glass produce a blotchy or snowflake pattern producing Snowflake Obsidian. Small nuggets of obsidian that have been naturally rounded and smoothed by wind and water are called Apache Tears

Collection

RAGM Mineral Collection

Acquisition

Accession

2014.1

Source or Donor

Crater Rock Museum (unknown donors)

Acquisition Method

Gift

Dimensions

Diameter

5 in

Location

Location

Cabinet

K-1 front

Wall

North

Building

Storage (old gift shop upstairs)

Category

Permanent