Black obsidian is a very powerful stone with a mysterious yet cleansing aura. It is commonly used for psychic protection, and it has the capacity to remove all the psychic smog that has been encapsulating its owner for quite some time. It also has powerful properties that can shield its user from negative auras and spirits. Posted by Doug on 1st Mar 2014. Frankly, I have less debitage to sweep up and dispose of when I buy flakes. Probably just me, but sometimes I get lazy and points are easier and faster to achieve with flakes. Double flow or banded obsidian from Montgomery Pass, NV is a unique obsidian with translucent gray/black and thin opaque bands of black obsidian running parallel which gives the appearance of looking through a Venician blind. As noted in the image shown, the parallel banding is easily seen for proper orientation for sawing.

• Raw Rock (Based on POUNDS; not by Piece)

Raw Rock (Based on POUNDS; not by Piece)

Product Description

**Disclaimer: If you are also ordering Slices(Slabs) or GROUND PREFORMS we suggest you DO NOT ship them with Raw Rock! If you take the risk we WILL NOT REFUND or RESEND MATERIAL!**

All rock prices listed are per pound, not per piece, unless requested.

Rock in its rawest form sold to you to start the knapping process.

If you're interested in getting rock from the quarry, please check out our 'THE QUARRY!' page.
**NOTE: Raw Keokuk Chert needs to be cooked to 585 to 600 degrees to work well. If you don't have a kiln you will most likely not be very happy with this rock raw.

Black Obsidian........................................................$1.50.

--Black Obsidian (100 lbs at $1.25 a pound)........….$1.25 lb.

--Black Obsidian (500 lbs at $1.00 a pound)...........$1.00lb.

Mahogany Obsidian………………………………......................$2.00 lb.

--Mahogany Obsidian (100 lbs at $1.50 a pound)....$1.50 lb.

--Mahogany Obsidian (500 lbs at $1.25 a pound)....$1.25 lb.

Banded Obsidian.....……………………………….$2.00 lb.

Silver Sheen Obsidian…………………………...$2.00 lb.

Rainbow Obsidian (2 Rocks to 1 lbs)...$3.00 lb.

Rainbow Obsidian 1 lbs-4.5 lbs ...........$5.00 lb.

Rainbow Obsidian 5 lbs-12 lbs (Min 5 lbs).…...…..$7.00 lb.

Dacite………………………………………………………..$2.00 lb. (Temporarily Out Of Stock) we still have dacite spalls

--Dacite (100 lbs at $1.50 a pound)...$1.50 lb. ^

--Dacite (500 lbs at $1.25 a pound)...$1.25 lb. ^

HEAT TREATED Keokuk Whole Rock…..$2.50 lb.

Raw Keokuk Chert………………………………….$1.50 lb.

Texas Flint………………………………………………..$2.75 lb

Georgetown Flint................4'-7' Tabs:$3.50 lb

Gold Stone………………………………………………..$4.50 lb.
Blue Gold Stone……………………………………….$7.00 lb.
Green Gold Stone……………………………………$7.00 lb.

Fine Grained Basalt.............................$1.50 lb.

(DISCLAIMER if you are unsure of Basalt, you may not want it right off the bat)

Striped Obsidian

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Overview

Obsidian is a volcanic glass of highly felsic composition that forms in lava flows which have undergone rapid cooling. The glass often contains ‘bands’ of alternating light and dark material – ranging in width from tens of microns to decimetres – which are defined by variations in crystallinity or vesicularity. Flow bands in obsidian are important because they preserve a record of deformation associated with magma accent, eruption and emplacement (Gonnermann and Manga, 2005).

Flow Banded Obsidian Formed

The presence of these texturally heterogeneous bands in compositionally homogeneous obsidian is well documented, but the features themselves are relatively under studied.

Glossary

• Obsidian – Hard, dark, glasslike volcanic rock formed by rapid solidification of lava without crystallisation.
• Microlites – tiny crystals with observable structure under the microscope.
• Vesicles– cavities formed by expansion of gas.
• Conduit – pipe or vent through which magma passes towards the surface.
• Textural heterogeneity – In this case, a rock texture which is non-uniform i.e. exhibits variability in texture over an arbitrary scale.
• Brittle deformation – ‘breaking’ of a material (in this case magma) when strain rates locally exceed the ability of the material to deform in a viscous manner.
• Viscous deformation – Irreversible deformation in a viscoelastic material (in this case magma). Viscoelastic materials strain when stretched and begin to return to their original state when stress is removed.

BANDING STRUCTURE

A summary of banding styles and composition is given in Figure 1. Banding is defined by alternating planar layers of varying colour as a consequence of varying microcrystallinity or microvesicularity (Gonnermann and Manga, 2005). As seen in Figure 1, the ‘darkness’ of bands is defined either by higher concentrations of microlites (commonly clinopyroxene and less frequently, oxides) or vesicles. Gonnermann and Manga (2005) use obsidian from Mayor Island volcano, New Zealand, as an example of banding formed from vesicles.

Figure. 1. Banded obsidian hand specimen (left) and the two main banding textures observed (photos adapted from Gonnermann and Manga, 2005). Microlite banding (top) refers to the subtle concentration of tiny, aligned clinopyroxene (cpx) and oxide microlitic crystals into dark colour bands in the glass. Banding is also caused by vesicularity (vesicle banding), in which case higher concentrations of vesicles in the glass may produce lighter coloured bands. Both band types are summarised schematically to the right of the microphotos.

A hypothetical physical process is proposed for the development of flow banding (Figure.2), based on the work of Gonnermann and Manga (2005).

Figure. 2. Schematic illustration of banding formation via brittle deformation of magma (Gonnermann and Manga, 2005). (a) Brittle deformation during simple shear; a tension gash style fracture is opened up in a fragment, and the grey area becomes a textural heterogeneity in the magma. This heterogeneity could represent either increased microlite content or vesicularity. (b) The fragments in the magma generated by brittle deformation become welded into a coherent piece. (c-e) Viscous deformation under simple shear in the magma deforms the brittle fracture into an elongate banded structure. (f) A second episode of brittle deformation occurs and the magma fragments through the banded structure. Repetition of this process reworks existing bands and produces more complex textural heterogeneities and finer banding structures.

DEFORMATION PROCESSES

Where To Find Green Obsidian

Brittle deformation

Brittle deformation (fragmentation) of magma can occur when strain rates locally exceed the ability of the melt of deform in a viscous manner (Figure 2a & f). This transition from plastic to brittle deformation is referred to as the glass transition (Webb and Dingwell, 1990). There is evidence to suggest that fragments formed from brittle deformation degass variably, and this may result in variable crystallisation kinetics over short distances (Hammer and Rutherford, 2002). Therefore, a textural heterogeneity (either microlite growth or vesiculation) is formed every time fragmentation occurs in the magma. When strain rates decrease in the magma, the fragments becomes welded and juxtaposed against other fragments, and deform plastically. Viscous deformation of texturally heterogeneous, welded fragments is inferred to be the mechanism which produces the banding structures we observe in obsidian. The process of brittle fragmentation and plastic deformation in magma can occur continuously during ascent or emplacement, and produces more texturally complex and thinner banded structures as reworking continues (Gonnermann and Manga, 2005). Similar processes of fragmentation are observed in shear zones, where banding is also observed (Otsuki et al. 2003).

Viscous deformation

The pervasive banding observed in obsidian requires repeated stretching and folding of the magma (Gonnermann and Manga, 2005), in which adjacent parcels of magma are transported and juxtaposed with each other (Figure 2b-e). In a highly viscous magma, viscous deformation is difficult to achieve without complex flow geometry (Voth et al. 2002), whereas brittle deformation occurs readily. Such complexity is difficult to model for rising magma at depth in the conduit.

Therefore, Gonnermann and Manga (2005) propose that the flow complexity is generated during surface emplacement (i.e. lava flows), or during ascent in the upper most part of the conduit (Figure 3). An important part of this idea is that microlite content may be higher on the edge of conduits, because the ascent rate is slower than in the centre of the conduit, and this textural heterogeneity is then deformed into bands during emplacement of the flow. Similarly, it has been suggested that variations in vesicularity may also be caused by variable ascent rates (Toramaru et al, 1996).

Banded Obsidian Properties

Figure. 3. Schematic theoretical model of flow band formation in a volcanic system. Variations in microlite content in obsidian may relate to increased crystallisation at the margin of the conduit, where the ascent rate is slower. The resultant textural heterogeneity is deformed viscously during emplacement (flows, domes), and the obsidian is stretched and folded to form bands .

Key ideas

• Banding in obsidian forms from the continual deformational reworking of magma
• The interplay between brittle deformation to produce fragments in the magma, and the complex viscous deformation during emplacement produce banding at a wide range of scales.
• Textural heterogeneity of either microlites or vesicles may be instigated by variable crystallisation within the conduit. When deformed, these heterogeneities become bands.

References

Gonnermann HM, Manga M (2005). Flow banding in obsidian: A record of evolving textural heterogeneity during magma deformation. Earth and Planetary Science Letters, 236, 135-147.

Aurora Borealis Obsidian

Dingwell DB, Webb SL (1990). Relaxation in silicate melts. European Journal of Mineralogy, 2, 427-449.

Banded Obsidian

Hammer JE, Rutherford MJ (2002). An experimental study of the kinetics of decompression-induced crystallisation in silicic melt. Journal of Geophysical Resources, 107, doi:10.1029/2001JB000291.

Otsuki K, Monzawa N, Nagase T (2003). Fluidization and melting of fault gouge during seismic slip: identification in the Nojima fault zone and implications for focal earthquake mechanisms. Jorurnal of Geophysical Resources. 108. doi:10.1029/2001JB001711.

Voth GA, Haller G, Gollub JB (2002). Experimental measurements of stretching fields in fluid mixing. Physical Review Letters, 88, doi:10.1103/PhysRevLett.88.254501.

Banded Obsidian

Toramaru A, Ishiwatari A, Matsuzawa M, Nakamura N, Arai S. Vesicle layering in solidified intrusive magma bodies: a newly recognised type of igneous structure. Bulletin of Volcanology, 58, 393-400.