What is it? Rock

[Ethan24]

I am reposting this previous post with better pictures. I found this rock in the badlands area of Eastern Montana. I was hiking through a mountainous area with my Grandfather. There was a lot of erosion in the area and this rock looked out of place to me. Can anyone help me identify what it might be? Thank you,

 

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[trk5capt]

Maybe A Hand Axe ? trk5capt...

 

[PBK]

Probably a preform— a roughly shaped piece intended to be worked further.

 

[trk5capt]

Probably a preform— a roughly shaped piece intended to be worked further.

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[Marty-Graw]

could it be volcanic rock? looks kind of glassy on the broken sections

 

[Kansas]

Have you ruled out that it might be a part of a larger fossil ?

 

[dg39]

Prehistoric beaver tooth?

 

[chong2]

is it obsidian??

 

[Cannonman17]

Wow, that is a lot better picture, now I would say the flaking scars are most definitely intentional. Exactly what type of artifact it is we could debate but here are your basic choices I think...
1)A preform of some sort, started and never finished into the desired shape- this is fairly unlikely though unless this particular material was abundant in the area where you found it. Quality quarried stone was typically too valuable to pick up and work on only to toss it later.
2) It may be a paleo period hand tool often referred to as a hand axe. This is quite likely and exciting because any artifact from the paleo period is quite rare, unfortunately it is also very difficult to prove that it's from the paleo period without some very close scientific study.
3)It may be a general purpose tool from a later period.
What you would need to do is take it to a close by university or similar and see if there is somebody there familiar with lithic use-wear analysis. By looking at the edges of such a tool under a microscope and comparing the wear patterns you can tell what it was used for (cutting wood, chopping bone, etc.)
If it is made out obsidian (I'm not quite sure from t he picture) it would be technically possible to date it also. In fact obsidian can be dated very accurately using a form of use-wear analysis. Obsidian actually "ages" or "oxidizes" for lack of wanting to go into great detail to a certain degree. As it does so you can see a line in the stone regress from the outer thin edges deeper into the stone, depending on how far it has moved will you give a good age estimate (it recesses at a known rate)

 

[norcalrockhunter]

It looks to me to be basalt a form of volcanic rock, we find alot of this rock out here, When we start finding it we are sure to find points, but the flaking on it looks to be more recent then old, look at the difference in color, it show no patina, yes this could be a preform, usually when we find pieces that big they scrapers uniface and some bi face. IMO

 

[Cannonman17]

I believe there is some patina on it, even on the flaking scars... I bet that if you accidentally broke the stone it would probably be jet black inside, a little darker than the flaking scars and much darker than the cortex.

 

[norcalrockhunter]

I will agree with you that if it was chipped right now it would have a much darker color then in the picture but if you look close at the first picture that is posted you will see little curly lines though it, that is typical of a piece that has not been worked (core) picture 4 shows it better. now on the other hand picture 5 has some old flaking, could this be from natives? or could it be from breaking off another rock?
The picture's that are shown IMO do not show any consist flaking, percussion flaking or secondary flaking, but does show some random flaking,
If its was found in or near a campsite then I would say it could possible be a crude scrapper, something that was used out of convince rather them something that was made for that purpose only

 

[Cannonman17]

I had to look again to see the curly cues you were talking about and now I see, the cortex - the original surface of the cobble. I am aware that a large portion isn't worked but thats not at all uncommon to see in crude bi-faces and the like. The flaking scars on the end are far too numerous in my opinion to be the result of some random collision with another rock. All the flaking scars appear to be made at the same time- for it to bump into another rock and result in a large flake is rare, for it to happen a dozen times or more I can't see. I won't argue the crudeness, it's definitely not a refined piece, in all likelyhood made and used once or twice and discarded or lost but intentional none the less.

 

[numnydar]

it does look like obsidian and I found obsidian arrow and spear heads in eastern Or. in my teen yrs also looks like the shape of a skinning edge...just my 2 cents

 

[JakePhelps]

flint? chert? obsidian? am i coming close? lol i have no idea what it is..but a nice find

 

[norcalrockhunter]

Basalt
Basalt is a hard, black volcanic rock with less than about 52 weight percent silica (SiO2). Because of basalt's low silica content, it has a low viscosity (resistance to flow). Therefore, basaltic lava can flow quickly and easily move >20 km from a vent. The low viscosity typically allows volcanic gases to escape without generating enormous eruption columns. Basaltic lava fountains and fissure eruptions, however, still form explosive fountains hundreds of meters tall. Common minerals in basalt include olivine, pyroxene, and plagioclase. Basalt is erupted at temperatures between 1100 to 1250° C.

Obsidian
Obsidian is dense volcanic glass, usually rhyolite in composition and typically black in color. Compared with window glass, obsidian is rich in iron and magnesium; tiny (<.005 mm) crystals of iron oxide within the glass cause its dark color.
Obsidian is often formed in rhyolite lava flows where the lava cools so fast that crystals do not have time to grow. Glass, 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 colors in obsidian result from the oxidation state of the chemical elements within the tiny minerals that are finely dispersed in the glass. Black color results chiefly from magnetite, Fe304. If the obsidian is highly oxidized, then the glass may contain hematite, which provides a reddish hue. Variations in the oxidation state of the iron (Fe) varieties imparts a slight greenish hue. Some obsidian is banded, a consequence of oxidation on a flow surface being folded into the lava as it continues to move.

 

[MD]

I have taken an interest in rocks and minerals in conjunction with nugget hunting. I have a few pieces of the same stone around and have identified it as obsedian. It is of volcanic orgin. It fractures in the way as shown in the picture (referenced cleavage, I think). It is glassy because it cooled very quickly. It is better than high quality steel for precision cutting. It was commonly used for prehistoric tool making. In fact it is still used by optometrists to make precision cuts in eyes. Thanks to the person who posted the detailed information on its chemical composition.

 

[norcalrockhunter]

I still think it is Basalt, I've been hunting rocks for a long time and always in the north west where Obsidian and Basalt are in abundance, there clearly have different charteristic's , if you re read my last post on Basalt and Obsidian it is clearly described the difference between the to

Basalt
Basalt is a hard, black volcanic rock


Obsidian
Obsidian is dense volcanic glass, usually rhyolite in composition and typically black in color. Compared with window glass