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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 # OBS17001 Mahogany Obsidian $12.00 |
Mahogany Obsidian Rough from Utah (photographed wet to show color)
This specimen weighs 1.3 pounds ( 593g ) and measures 4.2 x 3.5 x 0.8 to 2 inches thick (107 x 89 x 21 to 51mm)
This specimen weighs 1.3 pounds ( 593g ) and measures 4.2 x 3.5 x 0.8 to 2 inches thick (107 x 89 x 21 to 51mm)
| Item # OBS17002 Mahogany Obsidian $5.00 |
This specimen weighs 0.35 pounds ( 160g ) and measures 2.5 x 2.1 x 1.8 inches (64 x 53 x 46mm)
| Item # OBS17003 Snowflake Obsidian $5.00 |
Snowflake Obsidian Rough from Utah (photographed dry in its natural state)
This specimen weighs 0.54 pounds ( 249g ) and measures 2.6 x 2.4 x 1.8 inches (66 x 61 x 41mm)
This specimen weighs 0.54 pounds ( 249g ) and measures 2.6 x 2.4 x 1.8 inches (66 x 61 x 41mm)
| Item # OBS17004 Snowflake Obsidian XL Flakes! $12.00 |
Snowflake Obsidian Rough from Utah (photographed dry in its natural state) Extra Large Flakes!!
This specimen weighs 1.47 pounds ( 665g ) and measures 4.5 x 3.3 x 2.5 inches (114 x 84 x 64mm)
This specimen is face cut and shows the orbicular centers of the large pieces of cristobalite in this mix. This piece is
from the outer edge of a flow where the minerals did not get quite hot enough to fuse as thoroughly as they normally
do. A very unique specimen with the largest flakes we have seen. There are many fractures in this piece making it
most usable as a display piece. The specimen is solid, but would not cab well.
This specimen weighs 1.47 pounds ( 665g ) and measures 4.5 x 3.3 x 2.5 inches (114 x 84 x 64mm)
This specimen is face cut and shows the orbicular centers of the large pieces of cristobalite in this mix. This piece is
from the outer edge of a flow where the minerals did not get quite hot enough to fuse as thoroughly as they normally
do. A very unique specimen with the largest flakes we have seen. There are many fractures in this piece making it
most usable as a display piece. The specimen is solid, but would not cab well.
| Item # OBS17005 Large Tri Flow Obsidian $17.00 |
Tri Flow Obsidian Rough from California (photographed wet to show color) tan coloring is on surface only
This specimen weighs 3.4 pounds ( 1542g ) and measures 6 x 4.7 x 2.9 inches (15.6 x 12 x 7.4cm) Excellent specimen
for slabbing, knapping or display if cleaned. This piece is in its "as found" state
This specimen weighs 3.4 pounds ( 1542g ) and measures 6 x 4.7 x 2.9 inches (15.6 x 12 x 7.4cm) Excellent specimen
for slabbing, knapping or display if cleaned. This piece is in its "as found" state
| Item # OBS17006 Large Tri Flow Obsidian $18.25 |
Tri Flow Obsidian Rough from California (photographed wet to show color) tan coloring is on surface only
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
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
| Item # OBS17007 Large Tri Flow Obsidian (Split) 2 pieces $12.50 |
This specimen weighs 2.51 pounds ( 1142g ) and measures 5.2 x 3.8 x 2.5 inches (13.2 x 9.7 x 6.4cm) {Measured as
one whole piece} Excellent specimen for slabbing, knapping or display if cleaned. This piece is in its "as found" state
one whole piece} 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
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Shipping,
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combined
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totals
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| SOLD on its way to Avalon, CA |