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Arizona Rex

BIO-logic or GEO-logic?

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Arizona Rex

Found this on a desert walk southwest of Tucson, Az.  Cool find.....is it possibly some kind of fossil, perhaps a fossilized structure similar to septarian formations, or just a cool looking little rock?  Thanks for any and all help. :)

 

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Max-fossils
14 minutes ago, Tidgy's Dad said:

This looks like calcite boxwork, where the softer minerals between criss-crossing calcite veins has eroded away 

I don't know enough about mineralogy to confirm this specific ID, but if it is it would indeed prove to be geologic and not biologic in origin. Definitely looks like a bunch of cool crystals. Found similar ones in Southern France. Nice find :dinothumb: 

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Arizona Rex

The forum is such an awesome place!  Thank you so much gentlemen.  REALLY dig the quote from Mary Anning!! :trex:

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Darko

Cool crystals that's for sure! :)

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WhodamanHD

Desert rose methinks.

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DPS Ammonite

Looks most like massive quartz boxwork veins. The overall rounded shape of rock suggests that the rock is harder than calcite. @Arizona Rex, scratch rock with steel knife blade to determine hardness. A knife blade will scratch calcite but not quartz.

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ynot
1 minute ago, DPS Ammonite said:

Looks most like massive quartz boxwork veins. The overall rounded shape of rock suggests that the rock is harder than calcite. @Arizona Rex, scratch rock with steel knife blade to determine hardness. A knife blade will scratch calcite but not quartz.

I agree with this.

But it would still be classed as a boxwork.

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abyssunder

It's boxwork .

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Auspex
12 minutes ago, WhodamanHD said:

Desert rose methinks.

Well, similar looking, but different mineral and process.
Desert Roses are barite crystal growths, this boxwork specimen is a harder (prob. quartz) mineral structure that was exposed by the erosion of its matrix rock.

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abyssunder

" Boxwork can be composed of any mineral more resistant than the surrounding bedrock, which weathers away, but calcite is most common. Calcite protrudes as fins, plates, or veins in all limestone layers, but boxwork forms only in caves that have had long periods of intense weathering (Palmer 1984). "

 

" The combination of crystalline veins of calcite surrounded by crumbly, altered bedrock is necessary for the formation of boxwork. "

 

" Boxwork is a relic from the very earliest stages of cave formation (Palmer 1995). As such, boxwork is a speleogen, forming when bedrock between preexisting calcite veins were preferentially weathered away as the cave developed. The calcite veins (now fins) were originally gypsum (or anhydrite) that filled cracks in the dolomite; pseudomorphs of the original gypsum crystals are commonly preserved within these fins. The intervening bedrock is porous and crumbly, having been altered by sulfuric acid. In many places crumbly, weathered, brown or black bedrock still occupies the gaps between the boxwork fins. Altered bedrock between boxwork veins disintegrates and falls out at the slightest touch, especially in zones of condensation and periodic rises in the water table (Palmer and Palmer 1995). "

 

reference K. KellerLynn. 2009. Wind Cave National Park Geologic Resources Inventory Report, Natural Resource Report NPS/NRPC/GRD/NRR-2009/087

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WhodamanHD
36 minutes ago, Auspex said:

this boxwork specimen is a harder (prob. quartz) mineral structure

Not saying this is wrong, but how was it deduced?

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DPS Ammonite
51 minutes ago, WhodamanHD said:

Not saying this is wrong, but how was it deduced?

Regarding what both Auspex and I said: this is a boxwork probably composed of quartz. Tests with acid and a knife scratch should help determine the mineral.

 

A boxwork is a collection of a vein/crack filling mineral that forms many planes that are oriented in many different directions in 3-D space. Some of the planes curve and change directions.

 

Quartz is likely because it is a very common and durable mineral that is common in Arizona. The rounded outline of the rock suggests that it may have been tumbled in a stream. Quartz in much more likely to survive in a stream than the much softer and easily dissolved calcite. Again, tests should help us determine the mineral.

 

You, HodamanHD, thought that this was a desert rose (selenite or barite). Desert roses are crystals grown in unconsolodated sediment, often sand. The sediment often sticks to and is included in the crystals. The crystals are more uniform in size, thickness and shape than the veins in boxwork. Each crystal is in only one flat plane. Note that the veins in boxwork a abruptly change direction and curve. See pictures and article about desert roses:  https://en.m.wikipedia.org/wiki/Desert_rose_(crystal)

 

Maybe @Auspex has further insight on or a different take on this question.

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Auspex
41 minutes ago, WhodamanHD said:

Not saying this is wrong, but how was it deduced?

Because it has to be harder than the lithified matrix from which it eroded.

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WhodamanHD
18 minutes ago, DPS Ammonite said:

. Desert roses are crystals grown in unconsolodated sediment, often sand. The sediment often sticks to and is included in the crystals. The crystals are more uniform in size, thickness and shape than the veins in boxwork. Each crystal is in only one flat plane. Note that the veins in boxwork a abruptly change direction and curve

That makes sense, thanks for the info!

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MeargleSchmeargl

I'd go with GEO here.

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Max-fossils
On 4/15/2018 at 9:25 PM, Arizona Rex said:

REALLY dig the quote from Mary Anning!! :trex:

Haha, thanks :) I also love this quote!

 

Remarkable Creatures by Tracy Chevalier is a must-read for anyone into paleontology. Such an interesting book! Fair enough, it won't be very useful to ID your Peace River shark teeth or Alberta dino fossils, or help you ID anything for the matter, but the story is really awesome. Plus you do learn a lot from it: the difficulties for women in the early 1800s, the intolerance of the Church towards fossils, how life was back then, etc. Also, the best thing is that the story happens at the moment when people are starting to discover that the fossils they find are remains of creatures no longer alive... So this is the first time that people realize that extinction is actually a thing. A pretty scary thought if you've never known that would be possible! 

So yeah, because of all those things, it's an awesome book. Plus, there are so many fossils featured in it; what more could you possibly ask for? :P 

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digit
On 4/18/2018 at 12:17 PM, Max-fossils said:

So yeah, because of all those things, it's an awesome book. Plus, there are so many fossils featured in it; what more could you possibly ask for? :P 

How about the audio book form read by Sir David Attenborough? :)

 

I always take "what more could you possibly ask for?" as a challenge. ;)

 

I need to add that book to my reading list.

 

 

Cheers.

 

-Ken

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Max-fossils
20 hours ago, digit said:

How about the audio book form read by Sir David Attenborough? :)

 

I always take "what more could you possibly ask for?" as a challenge. ;)

 

I need to add that book to my reading list.

 

 

Cheers.

 

-Ken

Ooh, sounds interesting. Would love to hear that! :P 

Could you send me a link to it please?

 

Edited by Max-fossils
(Misunderstood the message)

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