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Author Topic: Black Sand...?..what's that all about ?  (Read 26520 times)

Offline neilep

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Black Sand...?..what's that all about ?
« on: 07/10/2007 19:36:41 »
Dearest Beach Dwellers Of Suntan Luff & Joy,

See this beach !!



nice eh ?

Notice how serene and exceedingly ' film noir ' the beach is !!

What's that all about ?......did someone just dump a load of granulated coal ?

I do not know...do ewe ?





 

Offline Karen W.

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« Reply #1 on: 07/10/2007 20:08:13 »
Here is one example of why perhaps there are other reasons also! Yours looks blacker!

http://en.wikipedia.org/wiki/Punaluu_Black_Sand_Beach

Punaluu Black Sand Beach
From Wikipedia, the free encyclopedia

A Green Sea Turtle resting on Punaluʻu Black Sand Beach (Photo: Lisa Weber)
A Green Sea Turtle resting on Punaluʻu Black Sand Beach (Photo: Lisa Weber)

Punaluʻu Black Sand Beach is a beach near Nāʻālehu on the Big Island of the U.S. state of Hawaiʻi. The beach has black sand created by lava flowing into the ocean which explodes as it reaches the ocean and cools. This volcanic activity is in the Hawaiʻi Volcanoes National Park.

Punaluʻu is frequented by endangered Hawksbill Turtles and Green Sea Turtles, which can often be seen basking on the black sand. Visitors must remain 15 feet from the turtles at all times. The swimming area is very rocky, and it can be dangerous to swim. The beach also has a large amount of underground fresh water that flows in it. This fresh water is very cold and looks almost like gasoline mixing with the water. Legend has it that in the time of drought, the early Hawaiians living in the area would dive underwater with a jug to get their fresh water.[citation needed]

Taking black sand and volcanic rocks from the area is prohibited.[citation needed]

Local tradition says that if any volcanic rock or black sand ifrom Punaluʻu Beach is taken away from Hawaiʻi, that the person that took it will be cursed by the Hawaiian volcano goddess Pele until it is returned. While purportedly an ancient Hawaiian belief, historians can trace this legend only to the mid twentieth century, and it is widely believed to have been invented by park rangers to keep visitors from taking rocks. Nevertheless, the lobby of Kīlauea Military Camp (now a vacation area for military personnel) has a cabinet displaying rocks returned by people attempting to atone for the bad luck that has befallen them, and letters describing their predicaments.

Russ Apple may have been the originator of this myth; as National Park Service Pacific historian and 30 year veteran of the National Park Service, Apple was instrumental in restoring Hawai'ian cultural resources in Kīlauea and Pu'uhonua o Honaunau National Historical Park in Kailua Kona, Hawai'i.[citation needed]

Camping is permitted at the Punaluʻu Black Sand Beach Park.
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Offline Alandriel

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Black Sand...?..what's that all about ?
« Reply #2 on: 07/10/2007 21:57:21 »
Black beaches are superb!

I love them almost as much as really white coral sand beaches.

Here are some more around the globe:


Playa Negrita / Black Sand Beach ~ Vieques Island, Puerto Rico


Dyrholaey,south coast of Iceland


Thaiti


La Gomera ~ Canary Islands / Spain



Funky!!!!



But - even more spectacular I find blue holes, this one in the Lighthouse Atoll / Blue Hole Belize



even  [8D]-er .................gotta love volacano's!  ;D


 

Offline JimBob

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« Reply #3 on: 08/10/2007 02:06:49 »
Black sand is the erosional product of basaltic rocks.
 

Offline Karen W.

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« Reply #4 on: 08/10/2007 03:25:20 »
Balsaltic???

Nice pics Alandriel!
 

Offline Alandriel

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« Reply #5 on: 08/10/2007 14:44:25 »

Basalt

Basalt is a fine-grained, silica-poor, igneous rock and is by far the most abundant volcanic rock. It ranges from black to dark gray in color. Most basalts occur in lava flows and sheets.
 

Offline Karen W.

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« Reply #6 on: 08/10/2007 15:39:38 »
Looks like lava rock to me! LOL LOL I did not know it had another name! LOL

OH.......Like this rather large chunk on me desk! LOL


 

Offline Bass

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« Reply #7 on: 08/10/2007 23:48:00 »
While your "chunk" is certainly volcanic, it is not basalt.  Rather, that is a piece of obsidian, or volcanic glass (you can tell by the conchoidal fracture and the lack of crystals).  Most obsidian is silica-rich, similar to rhyolite (at the opposite end of the volcanic spectrum from basalt) and ranges in color from red to brown to gray to black.
 

Offline Karen W.

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« Reply #8 on: 09/10/2007 01:52:33 »
Oh I thought they were one and the same just different names.. Thanks for the correction! We have always called obsidian Lava Rock and  I have never heard of the other!Thanks!
 

Offline JimBob

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« Reply #9 on: 09/10/2007 02:30:01 »
Rhyolite is just "granite" (or it's chemical equivalent) that has erupted to the surface. This rock cooled so fast it cooled as glass. It is a type of lava just not basaltic in chemistry.
 

Offline Karen W.

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« Reply #10 on: 09/10/2007 03:46:26 »
Thanks Jim for explaining the difference!
 

Offline Alandriel

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« Reply #11 on: 10/10/2007 21:36:30 »
Great info, Bass & JimBob

Nice piece of obsidian there Karen. Take care not to cut yourself. That looks very sharp.
Obsidian makes some lovely jewellery. I've used obisidan beads in the past. Lovely! :)

Another related question if you dont mind. I have this rock



quite heavy for its size, picked up from a high plateau in Sinai, a once volcanic region many aeons ago.
Now someone once told me that this was also volcanic, from slow moving lava, hardened quite slowly hence
that funny, knobbly appearance.

Expert opinion as what it is and approx. how old?
 

Offline Bass

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« Reply #12 on: 10/10/2007 22:18:12 »
Photo looks a little fuzzy- can you see distinct crystals, or is the rock just a mottled brown and white?  You mentioned the density, how hard is the rock?  Do you notice any vesicles (I couldn't see any in the photo)?  Where you found the rock, do you have any idea what the surrounding rocks were?  Was this part of an outcrop? lying on the surface?  Is the rock as shiny as it appears in the photo?
If it is volcanic, probably somewhere in the andesite to basalt range (assuming white flecks are plagioclase?), possible desert varnish gives it shiny appearance?
 

Offline JimBob

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« Reply #13 on: 10/10/2007 22:29:39 »
Oh, shite, is it a coprolite???
 

Offline Alandriel

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« Reply #14 on: 10/10/2007 22:37:03 »
Sorry, no crystals to see, just a kind of smooth, 'sandblasted' surface (which is not astonishing as I found it on a high plateau in the Sinai desert that has high winds).

Density? Yiikes no idea and I really don't want to scratch it.

When I say 'heavy' I meant, it's not light like many other volcanic / pumice type of rocks but has a good weight /size ratio.
 
Surrounding rocks? Well, it looks like a broken off piece that once had another probably smaller 'nobble' attached. I found it amongst many smiliar ones on that plateau, just lying around really.

It's not as shiny as the photo makes out I'm afraid, that's the light playing on the camera (though this pic is taken without flash). I'll try perhaps to get a better closeup piccie tomorrow.

No flecks, not specks, just pretty uniform in colour, dark brown, the creases have sand grains embeded in them.

Thanks guys for the interest! :)
 

Offline Alandriel

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« Reply #15 on: 10/10/2007 22:38:03 »
hmmmmm you know what, I just googled coprolite... and mine DOES look awefully much like that.

 ???... what is that?? Must google some more tomorrow. Nighty night and thanks again!
« Last Edit: 10/10/2007 22:40:01 by Alandriel »
 

Offline JimBob

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« Reply #16 on: 11/10/2007 02:36:00 »
I know that many areas in the Sinai have served as holy sites for many different peoples. If I remember correctly, the oldest standing stones in the world are found there. Are there any of these close to the site you found this rock?
 

Offline Karen W.

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« Reply #17 on: 11/10/2007 02:36:50 »
Great info, Bass & JimBob

Nice piece of obsidian there Karen. Take care not to cut yourself. That looks very sharp.
Obsidian makes some lovely jewellery. I've used obisidan beads in the past. Lovely! :)

Another related question if you dont mind. I have this rock



quite heavy for its size, picked up from a high plateau in Sinai, a once volcanic region many aeons ago.
Now someone once told me that this was also volcanic, from slow moving lava, hardened quite slowly hence
that funny, knobbly appearance.

Expert opinion as what it is and approx. how old?

You Know I had this huge beautiful white Doggie and I swear if I didn't

know better I would say that is one fine looking piece of petrified Dog

doo! LOL LOL!
 

Offline Bass

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« Reply #18 on: 11/10/2007 02:38:15 »
Oh, shite, is it a coprolite???
That was my first thought also- didn't know they were common on the Sanai ???
 

Offline Karen W.

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« Reply #19 on: 11/10/2007 02:40:48 »
Sorry I couldn't resist! LOL I will be careful with my obsidian! LOLIt really is not sharp at all its well worn on the edges!
 

Offline Bass

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« Reply #20 on: 11/10/2007 05:08:32 »
Karen, is your obsidian "chunk" from Newberry, or did you find it elsewhere?
 

Offline Karen W.

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« Reply #21 on: 11/10/2007 05:16:39 »
I found it in me daughters Yard! LOL! I do not know where it came from.... We are close  enough to drive to many different prospective places! LOL!
 

Offline Bass

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« Reply #22 on: 11/10/2007 05:24:08 »
No telling where it came from, then.  There is a massive, pure black obsidian flow in Newberry Caldera (Oregon)- some of the pieces I have from there look very similar.  Archaeologists have found pieces of Newberry obsidian on the east coast, so it must have been very valuable to the native american tribes- for pieces to have been traded all the way across the country.  Makes incredible arrowheads and cutting tools.
 

Offline Alandriel

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« Reply #23 on: 11/10/2007 14:53:50 »
***** pops back into the thread, a well-deserved after a hectic morning cuppa tea steaming at the side....
ahhhhhhhhh , finally a quick R&R break  ;D

googles coprolite

 :o :o

ahem......











how nice!






I might have a petrified piece of poo






 ;D ;D ;D ;D ;D ;D



jeeez, that nearly sent my cuppa flying!!



I know that many areas in the Sinai have served as holy sites for many different peoples. If I remember correctly, the oldest standing stones in the world are found there. Are there any of these close to the site you found this rock?

WOW! Now I'm impressed!

You know about the standing stones?

Not many people do .... I've seen a few around, here and there dotted around the most inaccessible places in Sinai
(I'm a bit of a desert enthusiast as you have probably gathered) but have not been able to find much info on them and
everyone I've asked to date just pretty much shakes their head. I thought it was my imagination......
Glad to hear I'm still (partially) sane  ;D

This particular piece of whatever-it-will-turn-out-to-be, well, it's quite possible I picked it up near just such a standing
stone. Or possibly not. I really don't know or remember at this point. You see, I'm in the habbit of always popping strange
looking rocks into my pocket pretty much where-ever I go...

so... hmmm..... it might still be an ancient piece of someone's dinner.... or perhaps not. The plot thickens!  ;D

I've taken another piccie - maybe this one's better?

 

Offline JimBob

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« Reply #24 on: 11/10/2007 17:56:06 »
Oh, it's a ram's head coprolite - those are rare!
 

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Black Sand...?..what's that all about ?
« Reply #24 on: 11/10/2007 17:56:06 »

 

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