Obsidian

Mahogany ObsidianObsidian is a rock which is a type of naturally occurring glass, produced by volcanoes (igneous origin) when a felsic lava cools rapidly and freezes without sufficient time for crystal growth. It is commonly found within the margins of felsic lava flows, where cooling is more rapid. Because of the lack of crystal structure, obsidian blade edges can reach almost molecular thinness, leading to its ancient use as arrowheads and its modern use as surgical scalpel blades.

While a rock like basalt is dark because of ferromagnesian enrichment, obsidian consists mainly of silicon dioxide, usually 70% or more. Obsidian is mineral-like, but not a true mineral because it is not crystalline. Its composition is very similar to that of granite and rhyolite. It is sometimes classified as a Mineraloid because obsidian is metastable at the earth's surface (over time the glass becomes fine-grained mineral crystals). The breakdown of obsidian is accelerated by the presence of water. Tektites were once thought by many to be obsidian produced by lunar volcanic eruptions, though few scientists now agree with this theory.

While pure obsidian is always dark in appearance, the color varies depending on the presence of impurities. Iron and magnesium typically give the obsidian a dark green to brown to black color.

Snowflake_Obsidi_105
Snowflake Obsidian
Snowflake_Obsidi_105 Snowflake Obsidian

Snowflake Obsidian

In some stones, the inclusion of small, white, radially clustered crystals of Cristobalite in the black glass develop a blotchy or snowflake pattern producing what is known as snowflake obsidian

Sheen Obsidian
Sheen Obsidian
Sheen Obsidian Sheen Obsidian

Sheen Obsidian

It may contain patterns of gas bubbles remaining from the lava flow, aligned along layers created as the molten rock was flowing before being cooled.These bubbles can produce interesting effects such as a golden or silver sheen, known as sheen obsidian

Rainbow Obsidian
Rainbow Obsidian
Rainbow Obsidian Rainbow Obsidian

Rainbow Obsidian

A multi-color rainbow sheen is known as Rainbow Obsidian and is a real favorite among collectors. Finished stones make striking displays.

Tri Flow Obsidian
Tri Flow Obsidian
Tri Flow Obsidian Tri Flow Obsidian

Tri Flow Obsidian

Another type of Obsidian has a mix of red/brown, black and clear swirls or layers in it. This type is called Tri Flow Obsidian. It is popular for knapping into arrowheads or knife blades.

Mahogany Obsidian
Mahogany Obsidian
Mahogany Obsidian Mahogany Obsidian

Mahogany Obsidian

Another popular type has relatively equal swirls of red, brown or golden coloring mixed with a black. This is referred to as Mahogany Obsidian as the swirls much resemble a woodgrain pattern.

 

 

Obsidian is relatively soft with a typical hardness rating of 5 to 5.5. Obsidian, unlike crystals, has no regular structure and therefore fractures in smooth conchoidal (curved) shapes. The intersections of these fractures can form edges sharper than the finest steel blades. For this reason, many modern surgeons prefer obsidian scalpels. Obsidian was historically used by many native cultures to make arrowheads and blades.

The Nevada, Utah and California area, referred to as the Great Basin, is an ideal location to find Obsidian. There are a myriad of colors, patterns and mixes of Obsidians, making them a very desirable collector item. The name Obsidian (from the Latin obsidiana) comes from Obsius, the name of the ancient Roman who discovered it in an African land that is today known as Ethiopia.

This Mahogany Obsidian listed Below from Glass Butte, Oregon tends to have a mix of layered clear possibly making it a combination of Mahogany & Tri-Flow

Mahogany Obsidian Rough
Mahogany Obsidian Rough
Mahogany Obsidian Rough Mahogany Obsidian Rough
Item # 28OBS01130650

Mahogany Obsidian Rough

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Mahogany Obsidian from Glass Butte in the high desert area of Central Oregon

(photographed wet to show color) weighs 1 lb 13oz or 1.8 lbs (830g) and measures 6.8 x 2.9 x 2.7" (17.2 x 7.3 x 7cm)

Mahogany Obsidian Rough
Mahogany Obsidian Rough
Mahogany Obsidian Rough Mahogany Obsidian Rough
Item # 29OBS01136170

Mahogany Obsidian Rough

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Mahogany Obsidian from Glass Butte in the high desert area of Central Oregon

(photographed wet to show color) weighs 2 lb 6oz or 2.38 lbs (1080g) and measures 6.4 x 3.9 x 3.1" (16.4 x 9.9 x 7.9cm)

Mahogany Obsidian Rough
Mahogany Obsidian Rough
Mahogany Obsidian Rough Mahogany Obsidian Rough
Item # 34OBS01131030

Mahogany Obsidian Rough

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Mahogany Obsidian from Glass Butte in the high desert area of Central Oregon

(photographed wet to show color) weighs 16oz or 1 lbs (460g) and measures 3.8 x 3.5 x 1.6" (9.7 x 9.1 x 4.1cm)

Mahogany Obsidian Rough
Mahogany Obsidian Rough
Mahogany Obsidian Rough Mahogany Obsidian Rough
Item # 35OBS01134630

Mahogany Obsidian Rough

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Mahogany Obsidian from Glass Butte in the high desert area of Central Oregon

(photographed wet to show color) weighs 1 lb 3oz or 1.21 lbs (550g) and measures 4.6 x 2.8 x 2.1" (11.6 x 7.1 x 5.5cm)

Notice

These specimens are relatively inexpensive to purchase but expensive to ship due to the weight. We ship US Post Office Priority Mail, Generally Flat rate boxes. We charge exact shipping cost + insurance cost + $3.00 for packing materials. Please consider buying multiple pieces as shipping is the same for 2 to 6 lbs and again from 6lbs to 10lbs. If multiple pieces fit in a flat rate box and you paid more shipping than is required we will refund excess shipping charges paid. Orders over 10 lbs may ship UPS Ground