Lava Rock

Jeann1

Jeann1

Joined
21 Dec 2010
Posts
830
Reaction score
18
Location
Witbank - Mpumalanga
Can I perhaps spark an interresting conversation about lava rock ?

I have been looking into this over the last few weeks, and have read loads of threads on the internet about different opinions.

basically what I have learned so far :

1 - Their is 2 types of "lava" rock - Ash that cools and forms rock like structures
Actual lava material that cools and hardens

2 - "Lava Rock" - Most rock beds under the sea is Lava Based - Lava is a mixture of granite and quartz... unlike popular believe very little if any metals are mixed into this.. 1 of the forms of metal is Pyrite (you would be able to see this with the naked eye as it is "fools gold" and makes gold colour deposits. Metals are heavier than most silica based geological matter (like quartz) and therfor

3 - "Ash Rock" contains melted / burned material that creates a pigment light enough to be clasified as "ash". This could be any of the natural occuring minerals found higher in the earths crust.. some of these minerals when melted / burnt can be toxic.

I am fortunate enough to have a Geologist for a dad (fater-in-law) and we took some samples of the commercialy available rock that you get...

White / Grey / Black Rocks ( or even a mix of these) - These lava rocks composition was 95 % Granite and Quartz (just remeber most sand is also quartz).

Red - Fairly high amount of oxides mixed with granite- thus the red colour

Brownish - Light Brown colour - more quartz than granite , with some minerals like silica and so on.

Dark Grey / Black - This is the one to be carefull of - mostly metals with very little granite.

This was a geological look at the rocks, not chemical.

Based on this a few points were made clearer -

1 - any if not all rocks found on earth is some form of lava - even calcuim based rocks came from the earths crust at some point.

2 - lava rock that is dangerous is very dark, or it will show clear signs of metals - like gold colour deposits (Pyrite - also contains arsenic trioxide arsenous anhydride arsenous oxide)

3 - The ocean floor is made of rock beds - "lava" material with a hardend and cooled crust constantly shifting .


Why I was interrested in this was Live Rock.. I bought some Live Rock and a few pieces broke off etc. and guess what - same geological matter as some Lava Rock

Interresting or what ?
 
@Neilh will be able to tell u the differences :) i could cut and paste and article but id rather not have the big man sit on me :)
 
Last edited by a moderator:
i have seen 2 marine tanks in cpt with lava rock with no problems whats so ever,in fact the 1 tank is running for 12years and looks stunning,i also did a lot of reading up infact i think the 1 website was garf and those guys no there stuff
 
It is way more complicated than your summary, unfortunately your logic is flawed. I will reply in detail tonight or tom to help clear up a few points
Posted via Mobile Device
 
Hi Neil, would love to here ,i read so much up on lava rock and yes about leaching bad stuff but still there is no real truth or am i incorrect by saying this,what i am going to do is set up a tank with lava rock and take it from there
 
Last edited:
taggin along
 
Hi All,

Jeann1, please take this in the light it is meant, i.e. informative, it is not an attack on the original post, just sharing some information.

First off let me say that I am not opposed to “lava rock” in a marine tank and I am not saying that lava rock in a tank will not work.

Lets deal with this term “lava rock” this is an extremely poor term, it is a bastardized geological term, in general the correct term would be basalt. So what is lava….. lava is molten rock, lava denoting the state of the rock (like solid water being ice) lava refers to the molten state (as ice refers to a solid state of H2O)……. The picture below is typical lava.
9114d52343c6da0b.jpg


It is clear that this term lava rock is creeping into the industry but lets call this basalt for the good of the geologists. OK so what is basalt and how does it form ? Well simply put there are two basic types of lava, lava that reaches the surface of the ground (meaning this can be below water level) and lava that does not. In general there are two further types of lava, felsic lave and mafic lava, felsic being minerals of composition that in general are light coloured and mafic being the dark minerals (in general).
Lets thus consider a felsic lava that does not reach the surface….. over millennia this molten mass cools down and forms a rock …..yes it literally can take millions of years to cool down…. if rock cools slowly it has a chance to do two things 1) is can segregate, thus concentrating minerals (such as platinum in the Bushveld igneous complex) and 2) in general it allows the individual minerals to grow within the lava, with my own eyes I have seen crystals the size of cars … a single crystal !!! look at youe average light coloured granite kitchen top and you will see large crystals, usually 2 white coloured crystals, the opaque one is plagioclase and the clear one is quartz, the smaller black or silver crystals are usually mica.
9114d5234040741b.jpg

a typical quartz, plagioclase and mica granite (in this case the mica is biotite)

Now consider basalt ….. basalt is generally a mafic lava (darker minerals) composed of pyroxene, olivine, magnetite, and ilmenite…. But the obvious difference between granite and basalt is the crystal size …. Basalt has a much smaller crystal size often we need a microcope to see the minerals, most times the rock has a dark green tint which comes from the olivine in the rock. In the so called lava rock we buy we get a whole bunch of holes in the rock and this gives the illusion of the rock being the same as live rock.
9114d523404156bc.jpg

Let me attempt to explain these holes, simply put, the lava containes gas pockets which try to escape the lava as it breaks through the ground….. if you look at a lava flow you will almost always see more holes at the top (called vesicles) these vesicles can even tell you the direction of the flow. An analogy would be something like oil mixed with water and then rapidly frozen … the oil will try to rize, if the ice forms too quickly then the oil would be trapped inside the ice. The composition of the material inside these vesicles is highly variable and could be harmless calcium or could be a far more devastating gas (here you need to think about all the poisionous gas escaping from a volcano… same thing this time however the gas may be trapped in the rock)
Holes are holes right? … well no …. Think of live rock which is, without going into huge detail, a calcium based sedimentary rock formed almost exclusively through 2 processes chemical precipitation of the calcium out of solution and predominantly through the calcification process of SPS and LPS corals …. Think on the interconnected tunnels that form as the living organism grows…. It is this interconnected system of tunnels and holes in Live Rock which makes it SUCH a good host for the bacteria we want in our marine tanks to aid in the nitrogen cycle. Now go back to the analogy of the oil and water….. in most cases I have seen these vesicles or holes are discrete holes and are not connected….. thus in GENERAL making a poor comparison to live rock. Having said that there must be cases where the holes are connected (things like pumice spring to mind) and in certain circumstance yes basalt may very well have holes which are connected …..

You stated that “Most rock beds under the sea is Lava Based” and you are correct, this process is as a result of continental drift, the process by which continents move apart. Basically as the continents move apart (eg South America moving away from Africa at about the speed your finger nail grows) a crack forms, in our example this crack is called the mid atlantic ridge, lava continually fills the gap, this lava is generally in the form of pillow lava. The images below show how the continents move apart and what pillow lava (basalt) looks like. Coral reefs on the other hand have nothing to do with basalt, they are calcium based and occupy, relatively speaking, very little of the ocean.
9114d523420cede6.gif

the evolution of the movement of the continents over time
9114d52343c72c67.jpg

the mid atlantic ridge
9114d52343c766a7.jpg

formation of basalt under water
9114d52344aca773.jpg

Typical pillow lava erupting under water
9114d523420d9605.jpg

Pillow lava exposed on land
Basalt can also form on the continents, these generally form as repeated eruptions from a “volcano” of sorts, in the south African context, the most obvious of the basalt flows is the Drakensberg, the layers we see denote repeated eruptions and resultant basalt flows (as an interesting side point, the most famous geological basalt flows are the Deccan traps in India which have been related by some scientists to the impact of a massive meteorite in the Yucatan peninsula (Mexico), the result was the extinction of the dinosaurs…. The ash cloud covered the earth, evidence in the form of illminite has been found in many parts of the world)
9114d5234041ac86.jpg

Lava flows with a very specific cooling temperature for these flows called columnar basalt
Now we understand what “Lava” rock is I will attempt to discuss some of your earlier points

1 - Their is 2 types of "lava" rock - Ash that cools and forms rock like structures
Actual lava material that cools and hardens. lava rock as with granite is an igneous rock, by definition a rock that formed from the cooling of a molten mass (granite stayed under the surface and cooled slower, basalt erupted in some form and cooled quickly). Ash on the other have cooled almost instantaneously and was then deposited on surface in a dry form, later compacted and solidified, this makes this a sedimentary rock, not an igneous rock, and therefore not comparable as different process are involved despite is seemingly common origin.

2 - "Lava Rock" - Most rock beds under the sea is Lava Based - Lava is a mixture of granite and quartz... unlike popular believe very little if any metals are mixed into this.. 1 of the forms of metal is Pyrite (you would be able to see this with the naked eye as it is "fools gold" and makes gold colour deposits. Metals are heavier than most silica based geological matter (like quartz) and therfor Granite is a type of rock, not a component of a rock, lava rock is composed predominantly of pyroxene, olivine, magnetite, and ilmenite, these are dark minerals and give the dark overall look of the rock. (granite is a rock composed of plagioclase and quarts, both light coloured minerals). In general I agree that within the rock itself there are not commonally many “impurities” however the vesicles are another matter and can contain many nasty things…. Granted however by the time the basalt makes it to our tanks these nasties have generally been weathered out of the rock

3 - "Ash Rock" contains melted / burned material that creates a pigment light enough to be clasified as "ash". This could be any of the natural occuring minerals found higher in the earths crust.. some of these minerals when melted / burnt can be toxic.

I am fortunate enough to have a Geologist for a dad (fater-in-law) and we took some samples of the commercialy available rock that you get...

White / Grey / Black Rocks ( or even a mix of these) - These lava rocks composition was 95 % Granite and Quartz (just remeber most sand is also quartz).

Red - Fairly high amount of oxides mixed with granite- thus the red colour

Brownish - Light Brown colour - more quartz than granite , with some minerals like silica and so on.

Dark Grey / Black - This is the one to be carefull of - mostly metals with very little granite.

This was a geological look at the rocks, not chemical.


The above is a set of generalizations which are so general that unfortunately do not hold true, the terms have been confused, I will not deal with them individually.

As an aside I remember one of my first lectures in mineralogy where the prof concerned stated that the colour of the rock itself was easily the least important aspect of deciding what the rock is, I laughed at this as it makes sense that the colour should be most important. Unfortunately for us, I have come to the same conclusion that the prof did…. Colour means very little, and the slightest impurity or change in a rock can change the colour and make the rock look like something completely different. For example we know quartz to be a clear coloured rock right (forget rose quarts for now) but smash a radioactive ray through the crystal and the structure will change to an opaque colour not dissimilar to plagioclase….. chemically the same, just the molecules arranged in a different way (and yes radiation like this occurs often in the natural world)

Based on this a few points were made clearer -

1 - any if not all rocks found on earth is some form of lava - even calcuim based rocks came from the earths crust at some point. This is an egg and chicken argument in the sense of which came first, I would say it is more correct to state that all compounds from gold to calcium and everything else was on this earth in a specific ratio, geological processes have simply concentrated different minerals in different area’s….. one of the ways calcium is concentrated is in the formation of coral reefs and the associated live rock. All rock can be classified as either igneous (from molten rock) Sedimentary (precipitation of minerals through erosion, chemical, physical etc) or metamorphic (when either sedimentary or igneous rock is deformed through pressure or temperature)

2 - lava rock that is dangerous is very dark, or it will show clear signs of metals - like gold colour deposits (Pyrite - also contains arsenic trioxidearsenous anhydridearsenous oxide) I have to disagree with this statement as previously discussed re colour, the ONLY way to be sure a rock is safe would be a suite of chemical tests and microscopic work

3 - The ocean floor is made of rock beds - "lava" material with a hardend and cooled crust constantly shifting . Correct, exclusing the coral reefs and of course deep sedimentary basins where we find amongst other things, oil deposits.


Why I was interrested in this was Live Rock.. I bought some Live Rock and a few pieces broke off etc. and guess what - same geological matter as some Lava Rock


It may have looked the same but proper live rock would have been calcium based and lava rock is igneous based, they are simply not the same thing, assuming it was proper live rock, a chemical analysis and or microscope would would have shown the difference.
I would like to say 3 more things
1) I categorically state that I am not saying lava rock will or will not work, I am simply pointing out the difference in origin and chemical composition. My opinion is that if any rock provides a spot for bacteria to colonize in useful concentrations it would be a valuable addition to a fish tank, provided of course that it has no nasties in the rock itself..
2) I am a geologist and have given a very simplified version of this, simplified to the point where another geologist would have problems with some of my generalizations, I have made these generalizations in the interest of conveying the underlying message and not in the interests of making everyone on MASA a geological expert
3) Crispin you are not getting the nennie back !
 
point 4: i am going to chop that nemmie :)

very cool explanation again, can you paste it in your rock thread as well
 
Very educational indeed.

Thank You. This is why I mentioned that its a geological look at it, not chemical. But even looking at it Geologically is more difficult that simply looking at it. (we basically broke pieces off and had a look with a micoscope)

So bottom line here is , adding Lava Rock to a marine aquaruim is dangerous because of the unknow factors involved, only if you can chemically sample and test what is actually in the rock, and you are fully aware of it, then only can it be used.
Am I right in saying this?

Might be worth a mention that my name is Jean :thumbup:
 
@Neil H
That must be one of the longest replies ever, and I read the complete reply, no spead reading...

What about the lava rock in the Koi world, those light weight little pieces that is man made (as far as I know). Mostly used in the filtration systems. Basically used because of their great surface area they provide for bacterial growth. How would you (Neil H) rate them.
 
Last edited by a moderator:
Nice explanation!

I work on coral reef accretion and am looking at ways of measuring it. Would you have any thoughts on this? Cores area a no-no. Far to difficult on our reefs and high-energy coastline.

The thinking is that SA reefs should be forming in a unconsolidated manner yet this does not seem to be happening.
 
I think the lava rock most reefers refer to is the once Riaan mentiond. It is basically clay, mixed with sticks, leaves etc, and then baked. Once baked, the sticks and leaves etc burns out, creating tiny holes, and making the "rock" brittle.

I was once warned about it when I started my very first tank with it. We cannot post links from s a r k , so can unfortunately not direct you to the thread and photos:

But, here is an old pic of my previous setup:

231120061042.jpg



This is about the only one I can find, showing the Lava rock at the background.

The stuff gave me endless problems wrt phosphates


030920071393.jpg
 
Jeann1 said:
Very educational indeed.

Thank You. This is why I mentioned that its a geological look at it, not chemical. But even looking at it Geologically is more difficult that simply looking at it. (we basically broke pieces off and had a look with a micoscope)

So bottom line here is , adding Lava Rock to a marine aquaruim is dangerous because of the unknow factors involved, only if you can chemically sample and test what is actually in the rock, and you are fully aware of it, then only can it be used.
Am I right in saying this?

Might be worth a mention that my name is Jean :thumbup:
Click to expand...
My personal opinion with regards to the reef stucture we use in our tanks is that it supplies the lungs and the majority of the biological fltration of our systems. Thats to say Live Rock or bio rock or lava rock or egg crate or play sand or aragonite (you get the picture) which we use as the structure of the reef are also the basis of our biological filtration.

With LR being the best structure to house bilogical filtration that we have at the moment i feel that using inferior (to what ever degree) biological filtration does little to help the tank. The analogy of LR being the *lungs* of a system allowing for the largest area of nitrogen cycling and thus id use the best quality LR i can afford.

denser material allows for less water penertration, lower biological activity and takes up greater space within the tank and thus reduces the systems ability to process waste.

Personally i believe in spending hard earned cash on the best quality bilogical filtration i can, simply LR and good aragonite.
 
Neil H said:

9114d523420cede6.gif

the evolution of the movement of the continents over time
9114d52343c72c67.jpg

the mid atlantic ridge
9114d52343c766a7.jpg

formation of basalt under water
Click to expand...

Hi Niel,

I just saw this post and a few things I don't really agree with, the Pangea theory is wrong, for it to work, you have to shrink Africa 30-40%, you have to remove all the countries between North and South America, it just does not fit. Also the years that are added in there, are wrong, I think if you start looking at the solar system, it definatly proves we living in a young earth.

I believe the continetal formation via chambers of water that broke under the upper layer of a granite crust, and a lower basalt layer. This exlpalins the continetal shelfs, mountain ranges that all run paralell to the oceanic trenches, and the fault lines. It even explains water in space, clams on everest, the geologic column, the ice ages etc.

Neil H said:



Based on this a few points were made clearer -

1 - any if not all rocks found on earth is some form of lava - even calcuim based rocks came from the earths crust at some point.
Click to expand...

I think if you look at the Polonium Halo effect in Granite, it is further proof that the world was never in a heat form.

Excuse the defence, the reply, the argument, I am sorry my bud, especially only seeing this post now, but I am a creationist, and I just feel I can't let some of my views go buy undefended.
 
You must log in or register to reply here.
Back
Top Bottom