| Obsidian |
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Obsidian
Obsidian 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. 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
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
or a multi-color rainbow sheen known as
Rainbow Obsidian
Another type of Obsidian called
Tri Flow Obsidian
has a mix of red/brown, black and clear swirls
in it making it popular for knapping.
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, obsidian was 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.
| Item # OBS07110105 Mahogany Obsidian $10.00 |
| Mahogany Obsidian Rough from Utah (photographed wet to show color) Specimen weighs 0.86 pounds ( 393g ) and measures 4.5 x 2 x 2.2 inches thick (11.4 x 5.2 x 5.6cm) |
| Item # OBS17006 Large Tri Flow Obsidian $18.25 |
| Tri Flow Obsidian Rough from California (photographed wet to show color) This specimen weighs 3.65 pounds ( 1654g ) and measures 5.6 x 4.4 x 3.4 inches (14.2 x 11.2 x 8.6cm) Excellent specimen for slabbing, knapping or display if cleaned. This piece is in its "as found" state |
Click on any photo to see a larger version
 |
| Item # OBS07111105 Mahogany Obsidian $8.00 |
| Mahogany Obsidian Rough from Utah (photographed wet to show color) Specimen weighs 0.55 pounds ( 251g ) and measures 3.9 x 1.8 x 1.7 inches thick (9.9 x 4.6 x 4.4cm) |
| Item # OBS07110205 Mahogany Obsidian $9.00 |
| Mahogany Obsidian Rough from Utah (photographed wet to show color) Specimen weighs 0.58 pounds ( 263g ) and measures 3.7 x 2 x 1.2 inches thick (9.4 x 5.2 x 3cm) |
| Item # OBS07110304 Mahogany Obsidian $6.00 |
| Mahogany Obsidian Rough from Utah (photographed wet to show color) Specimen weighs 0.28 pounds ( 126g ) and measures 2.4 x 2 x 1.1 inches thick (6.1 x 5.1 x 2.8cm) |
| Item # OBS07112221 Large Tri Flow Obsidian $20.75 |
| Tri Flow Obsidian Rough from California (photographed wet to show color) This specimen weighs 3.77 pounds ( 1708g ) and measures 5.7 x 4.4 x 3.5 inches (14.4 x 11.3 x 9cm) Excellent specimen for slabbing, knapping or display if cleaned. This piece is in its "as found" state |
| Item # OBS07111121 Large Tri Flow Obsidian $23.00 |
| Tri Flow Obsidian Rough from California (photographed wet to show color) This specimen weighs 4.17 pounds ( 1892g ) and measures 5.2 x 4.6 x 3.8 inches (13.4 x 11.7 x 9.7cm) Excellent specimen for slabbing, knapping or display if cleaned. This piece is in its "as found" state |
| Notice These specimens are relatively inexpensive to purchase but expensive to ship due to the weight. We only 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 |
| Notice to Our Customers We will be closed from May 18th through August 15th 2012 to relocate our business. Orders placed during this time will not be shipped until after August 15th. Purchases or Reservations will be honored in the date order they are received. 1st purchaser is served 1st. |