# Sticky  A Guide to Rocks in the Aquarium



## Jamblor

Hello everyone,

This thread will contain information on the different types of rocks that are commonly found around you, or in the aquarium. The hopes of this guide is to inform everyone on the types of rocks that are safe for your aquarium, and to give you a better sense of the world around you.

There will be different posts for different sections of this guide. They will be:

*1. The major rock groups: Igneous, Sedimentary, and Metamorphic.*

*2. Finding rocks in the GTA, and their composition. *

I hope you enjoy it and find some useful information. If there are any questions feel free to post here. Or if there is some other subject that you want information on I can try to post the answers here or at least direct you to some other sources.

While I do my best to provide accurate information here, I'm still only studying geology and therefore I am likely to make errors. Any information here should be taken with a grain of salt and my main goal is to give you a greater sense of rocks whether you buy them or collect them for your tank. Always wash/boil or disinfect any rocks you plan to use in your aquarium and if in doubt, don't take the risk.


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## Jamblor

*1. Igneous, Sedimentary, and Metamorphic Rocks*

*1. Igneous, Sedimentary, and Metamorphic Rocks*

To start off with, one should have a basic knowledge of minerals, the 3 rock groups and a general overview of the rock cycle.

---
*Minerals*

Minerals are defined as a substance that is naturally forming, has a measurable crystalline structure, and a definite composition. 
Many of you may be familiar with quartz crystals. 








This is the most abundant mineral in the crustal earth. It is very versatile and readily binds to other elements to form other major rock forming minerals.

The other rock forming minerals that you may come in contact with are:
Potassium Feldpar, Plagioclase, Amphibole, Biotite, Muscovite, Pyroxene, and Olivine.

In general, all you need to know is that minerals are found in rocks and they tend to form with other specific minerals based on the rock type. 

In the aquarium. If you decide that having crystals suits your taste note that all of the minerals that are listed above can be found or purchased. However, gem quality specimens tend to carry a hefty price. But if you happen to have some by all means use them. **Do NOT however use the following minerals: 
Calcite(contains calcium that can affect water parameters)
Dolomite(same as calcite)
Galena(not sure if it will affect the water but it is the primary ore for lead)
Sulfur(Appears yellow, it's sulfur.)
Talc(very soft and will likely break down in water)
Gypsum(same as talc)
There are others, however you probably won't come into contact with them. Your best bet is to stick to quartz.

---

What is a rock. A rock is a defined as an aggregate of specific minerals.

*Igneous Rocks*

The first type of rock I will discuss are Igneous rocks. Igneous rocks are volcanic in nature and form by cooling of a liquid magma. There are 3 general types of igneous rocks:

Intrusive/Plutonic - These rocks are formed by the relatively slow cooling of a liquid magma beneath the Earth. This magma has not penetrated the surface of the earth and thus produces some very nice and in some case very large crystals of specific minerals.

The most common intrusive igneous rock to most people is Granite. Granite is found everywhere today. From decorative stone to your counter tops(most however aren't actually granite). Granitic rocks have a varied, but generic composition and texture. 
Texture - Granites tend to have individual mineral grains that are large enough to be seen with the unaided eye. They range from 2-3mm grain size up to 10mm. Beyond 10mm it is known as a pegmatite. 
Composition - Granites tend to be felsic(comprised of feldspars and silica) and thus usually contain some combination of quartz, potassium feldspar, plagioclase, and amphibole. Some do contain other minerals, usually biotite.

Here are some pictures of granites:








The white is plagioclase, pinkish colour is K-feldspar, dark greyish is amphibole, and the grey translucent is quartz. This specimen is approx. 10cm across.









This granite has a little coarser grains, colours still match as the previous example however it is dominated by K-Feldspar.

Beyond granites, there is diorite and gabbro. Diorite looks similar to granite however it lacks the K-feldspar and some of the quartz. Because of this the rocks grains are usually white and black. Gabbro is similar to diorite byt is a lot darker.

Extrusive/Volcanic - These rocks have similar composition to granite, diorite, and gabbro. The main difference is that their grain size is very fine and usually takes a microscope to see the individual grains. They come from volcanic eruptions and lava flows. The cool rapidly thus the minerals don't have time to grow.

The most common extrusive igneous rock is probably basalt. Basalt is chemically identical to gabbro. Containing plagioclase, pyroxene, olivine, and other accessory minerals. Here are some pictures.








Always black or dark grey. If you look really closely you can probably see some larger crystals of the green mineral olivine.








This is an example of vesicular basalt. Lots of gas has created bubbles in the magma as it cooled. Your typical volcanic rock, it will have a rough and sometimes sharp texture.

There are a lot of different varieties of extrusive volcanic rocks such as rhyolite and andesite. However most people won't ever come in contact with these.

Pyroclastic - These rocks result from a volcanic eruption and consist of the ash fall and debris from the eruption. The fall or flow back to the earth and consolidate and weld themselves into a glassy rock.









Pumice can come in a variety of colours. It is rough, glassy, and sharp. This particular rock is very very light and can float on water!








Obsidian, made of pure volcanic glass. The edges are very very sharp. Usually black in colour.

These are just some of the more common examples of igneous rocks.

In general, igneous rocks are formed from the cooling of magma. 

In the aquarium. Igneous rocks are safe and are probably one of the more popular rocks, especially granites and basalts. As far as I know they are safe for aquarium use.

The next entry will be common sedimentary rocks.


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## Jamblor

*Sedimentary Rocks

*Sedimentary rocks are rocks that consist of consolidated sediment. Through the process of weathering and erosion of all types of rocks, sediments accumulate and eventually cement themselves together.

Sandstones are sedimentary rocks that consist of tiny grains of sand, usually silica but also can consist of hornblende and feldspars. They can be a variety of colours from earthy colours to various shades of red and green. There texture is similar to that of a medium to fine grained sandpaper. If you try and break them, their fracture is irregular and is kind of random.Sandstones might affect water parameters if the cementing grains are calcite rather than quartz. To check you can drop some dilute hydrochloric acid or vinegar on the rock and watch to see whether or not any fizzing occurs. If it fizzes it has calcite.
Here are some examples:








A typical sandstone has 'bedding' in which layers of different colours and sometimes grain size can be seen. 








Another common example with bedding absent.

Shales siltsones, and mudstones are the next most common example. They are similar in composition to sandstones however, the grains have been weathered significantly so as they are very fine. The colours again vary from browns, greys, and greens. The textures feel smooth to slightly rough, but not as rough as sandstone. These rocks are made of clay and while their original depositional environment likely involved being underwater at some point, they may deteriorate over time.
Here are some examples.








This is a shale. They are typically this colour. Fine grained and smooth. You know its a shale if you can see layers. The rock will fracture along these layers easily. Shale is the un-metamorphosed version of slate.








Similar grain size to a shale, however these rocks don't fracture a long layers.

***These next rocks contain calcite in some form or another which will affect water hardness.***

Limestones and dolostones are fine grained rocks consisting of calcium carbonate or magnesium-calcium carbonate. The individual grains are cemented together by calcite either in clasts or as microcrystalline grains. Limestones will tend to be chalky.
Here are some examples:








This limestone has a very fine grain size. If you look carefully you can see some imprints of fossils in the lower half.








Another limestone, different colour.

Conglomerates and Breccia are sedimentary rocks that consist of varying grain sizes cemented together with calcite. They contain pebbles and rock fragments. Here are some examples.








A pebble conglomerate.

In general, sedimentary rocks consist of various sediments cemented together.

In the aquarium. Sedimentary rocks contribute to a natural river or marine environment, however caution must be used when the rocks contain calcite. While rocks containing calcite will affect water hardness this may be what you are looking to do. Shales and mudstones are generally okay underwater but they are formed from clay and may soften and deteriorate over time. 

The next post will contain information on metamorphic rocks.


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## Kerohime

This is awesome, I almost took a geology class just to learn things like this, thanks for this post!


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## Joeee

This deserves a sticky =]


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## pat3612

Great write up lets sticky.


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## Jamblor

Thanks everyone! There is still a lot more to come. I'm about to start the writeup on metamorphic rocks. And hopefully on the weekend or Friday I can writeup the subsequent guide to rocks you can find in the GTA.


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## Jamblor

*Metamorphic Rocks

*Metamorphic rocks are rocks that have gone through some sort of change, typically from additional heat and pressure being added to their original or 'parent' rock. This change sometimes results in new minerals being added, and/or different properties of the rock.

The most common metamorphic rocks are listed below:

Slate is the daughter product of a shale. As discussed previously shale is a sedimentary rock consisting of clay. When intense pressure and heat are applied to shales they compress further and they also pick up a new mineral called muscovite. Slate looks very similar to shale except that in light you will notice a slight 'sheen' to the surface. This is from the addition of muscovite. Here are some examples.








Notice how this looks like a shale, but also notice that it is shiny rather than dull.

Schist. If you take a shale and expose it to a higher degree of metamorphism you will achieve a schist. Compositionally, schists are very similar to slates. However, they will be even shinier due to more muscovite and they tend to also pick up another mineral called garnet. Here is in example.








It's kind of hard to notice, but schists tend to still have a layered texture. As you can see, this is much more shiny and those black dots scattered throughout are the garnets. If you look closely at an actual sample they will be a brownish-red colour.

Gneiss. Gneiss is a highly metamorphosed version of a granite or possibly diorite. They tend to have the same minerals but in deformed and smaller grains. They will almost always have typical banding and different coloured layers. They however, will not fracture along these layers readily. The textures is similar to a coarse sandstone. Here are some examples.








You can see that it looks very similar in colour to the granite in the igneous section, but notice that the grains are lineated into layers. 








The colours can vary quite a bit, but they will always typically have the characteristic lineation across the rock.

Marble. Marble is a metamorphosed version of a limestone or dolostone. For the same reasons as listed in the sedimentary section, marble consists of calcite which can affect water parameters. Here is an example.








Marble is usually smooth and chalky, a variety of colours can be found. It will also fizz when acid is applied.

Quartzite. Quartzite is the metamorphosed version of a quartz sandstone. Basically all the quartz grains have been compacted together very tightly. Quartzite may sometimes be confused with marble, however quartzite is quite a bit harder than marble and it doesn't react with acid. Here is an example.








Even I have trouble distinguishing this one sometimes.

In general, metamorphic rocks are deformed versions of sedimentary and igneous rocks. They have been subjected to heat and pressure over time.

In the aquarium. Metamorphic rock are typically good to use in the aquarium, especially slate. The extra pressure these rocks have been subjected to make them quite inert and not prone to deteriorating over time. Some such as the gneiss can have nifty patterns to them.

So that's the basics and the most common types of rock that a person usually encounters. There are many many others and if you have questions on a specific rock I can try and answer them.

They next entry will focus on the rocks you typically see in and around the GTA.


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## dspin02

this is sweet. thanks for the awesome write up. looking forward to the upcoming rocks found in the gta.


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## KhuliLoachFan

My favorite kind of rock for cichlid tanks:

Lava Rock, is technically not rock, I guess. It's a volcanic pumice, is usually red. It's porous, making it much lighter than solid rocks would be in water, and also, seems to help buffer pH.


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## Jamblor

"Lava rock" is a rock. It is a form of igneous rock under the subcategory of pyroclastic debris. However the above picture isn't pumice.(unless it floats) Lava rock is the generic term for scoria. Scoria and pumice look very similar but scoria will have a density greater than 1 g/cm^3 while pumice is less than 1. 

Both rocks form the same way. Ejected magma rapidly cools, depressurizes and degasses forming the bubbles. Also the reddish colour will typically come from oxidation of iron bearing minerals in the magma.

Rocks are fun


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## impalass

Excellent post, thank you for sharing.


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## Jackson

What does lava rock do to ph? Will it raise it or not?

This is a great thread thanks for creating it.


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## Greg_o

This is great, thanks.

We have so many eperts here, and we now have a resident rock expert!


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## Jamblor

Well if it is natural lava rock(scoria) to my knowledge it shouldn't do anything to pH. I don't believe water has enough acidic/basic properties to actually dissolve the minerals in a scoria.


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## Jamblor

*Rocks in the GTA*

This post and successive posts will outline the specific types or rocks you are likely to find in and around the GTA.

Unfortunately, the native country rock that we sit on are Palaeozoic sedimentary rocks. I say unfortunately because sedimentary rocks are the type of rock that, over time, will affect your water parameters.

Below is a section of a geological map for the GTA. The different colours represent the contact between different rock formations.









East of Toronto, the green colour is the Ordovician(~500-435 million years ago) Whitby Formation which consists of different coloured shales. 
Toronto is right in the middle of Ordivician Georgian Bay formation. It consists of shales, limestones, dolostones. 
Westward to Mississauga. The grey colour is the Ordovician Queenston Formation, consisting of a red shale and some limestone.
Further west towards the Niagara Escarpment we encounter the Silurian age(435-412MYA) Cabot Head, Manitoulin, and Whirlpool Formations. All consist of different coloured shales, limestones, and sandstones. 
The orange colour, is the cap rock of the escarpment and is the Silurian Lockport & Amabel Formation which consists of grey and brown dolostone.

In this part of Ontario, the further West you go, the younger the rock formation.

So what does this all mean. It means that the majority of native rock you see in the GTA will be either a dolostone/limestone, a shale, or a sandstone. None of which are particularly desirable in an aquarium unless you don't mind the gradual increase in water hardness and alkalinity. 
 
BUT! it's not all bad news. If any of you travel North in the summer to a cottage that is in the Muskoka region. You have entered Precambrian(500-1000+MYA) rocks. The dominant rock there is Gneiss. Gneiss as mentioned early is a metamorphic rock. And possibly some granitic intrusions here and there.

AND! more good news. Thanks to glaciers in the last ice age, rocks from the North have hitched a ride and been deposited into the country rock and sediments of the GTA. That is why occasionally you will see granitic or gneiss type rocks kind of randomly appearing with the younger sedimentary rocks of the GTA. You can find these pretty much anywhere but you likely have to dig. The alternative is scouring the shoreline of Lake Ontario. Many of the cobble beaches in the GTA have abundant weathered cobbles of pink granite and gneiss. I would post examples but unfortunately my girlfriends backyard(my favourite rock place in the GTA lol) is encased in ice. But as soon as I can get some I'll post pictures of the examples.


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## Jamblor

Ok so I found some examples in the Geology Lab.
Sorry for the low quality pictures they are on my cell phone.









This is a grey shale. It is likely to not affect water parameters, however it is a relatively soft rock and may deteriorate over time.









An example of a Pink Granite. You will likely encounter this in a more smoothed and weathered version. Aquarium safe, very inert.









A banded gneiss. A metamorphic rock that is safe and inert. I think they look pretty neat. Again, you will likely find a rounded, weathered version unless you head up North.

These are a few examples I'll post more when I can locate some.


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## dspin02

this is great information, thanks a bunch. im up in the muskoka area a few times every summer, next time ill look for some cool rocks for my next tank.

if it hasn't been already, i think this should be stickied.


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## Jamblor

dspin02 said:


> this is great information, thanks a bunch. im up in the muskoka area a few times every summer, next time ill look for some cool rocks for my next tank.
> 
> if it hasn't been already, i think this should be stickied.


No problem  I get a lot of info from this community so this is my way of contributing.

And how do I get this stickied? Does an admin do it?


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## dspin02

Jamblor said:


> No problem  I get a lot of info from this community so this is my way of contributing.
> 
> And how do I get this stickied? Does an admin do it?


An we thank you for it, still looking for a way i can contribute, maybe sometime down the line.

and yeah, i believe admin/moderator's are the only ones who can sticky threads. im sure one of them will soon, this is a really good piece, people are always asking/wondering if rocks are safe or not, now we have a guide to refer to.


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## Jamblor

I found another very good example of what the granite found in the GTA will look like while browsing Van Beek's Garden Supply.


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## Kajendra

This stuff is so useful and an amazing read :/
Definitely should be stickied


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## Jackson

I spent 5 hrs looking through all the rocks I have and separated all the ones I thought were not safe using this guide. I then did vinegar tests and I was 100% with all the good and bad ones.

Thanks a lot man this is the best thread I've seen in years.


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## Jamblor

Jackson said:


> I spent 5 hrs looking through all the rocks I have and separated all the ones I thought were not safe using this guide. I then did vinegar tests and I was 100% with all the good and bad ones.
> 
> Thanks a lot man this is the best thread I've seen in years.


Wow! I'm glad to see that people understand everything I wrote  And good job getting everything right!


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## Ciddian

Ooooooop! Sooo sorry I have been slow! I agree.. Lets get this stuck!

Thanks for the great write up!


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## cichlidspiro

*list of where to find*

very nice article you have you seem very smart.
i was wondering if you could tell us where a good spot to find some of these rocks would be


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## Scotmando

What kind of rocks are these? 

Are they "aquarium safe"? I can provide a sample if needed.

I haven't tested them yet. I'll try the vinegar test.

They were collected in Saint Ferdinand, Quebec

Latitude, Longitude
46.13988,-71.599274

Thanks, Scott


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## JayPetro

Scotmando said:


> What kind of rocks are these?
> 
> Are they "aquarium safe"? I can provide a sample if needed.
> 
> I haven't tested them yet. I'll try the vinegar test.
> 
> They were collected in Saint Ferdinand, Quebec
> 
> Latitude, Longitude
> 46.13988,-71.599274
> 
> Thanks, Scott


Hey scott,

This appears to be phyllite, (similar to slate) which is a result of metamorphosis of shale or pelite. It does contain calcitic properties, as noted by the whitish crystal nodules. This may alter established tank parameters, such as altering pH and KH.

Jay
Geologist


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## Jamblor

I definitely agree with Jay, and as for collecting if you go down to any cobble beach on Lake Ontario just look for any of the pink rocks. They are granite.

Otherwise, you'll have to go North of Barrie to find some gneiss or granites in the form of pegmatites.


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## Egonsgirl

I have a question..... what if someone had access to a process of high heat (hot enough to harden steel), would it be possible to alter any of these other rocks, that are similar to slate, but not recommended for our tanks???? Thanks for the awesome info.


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## JayPetro

Heat is just one element needed to alter rocks, but it is the combination of intense heat and more importantly intense pressure which is not usually achievable under normal atmospheric conditions so I doubt that you would be able to alter any rock solely based on heat.


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## garwood

*safe rocks*

i have some large stones called frontenac natural weathered stone that were used in the backyard. does anyone know these stones and are they safe. i tried some vinegar but couldnt tell if bubbles were forming. i like the look with cracks( fissureslooking attributes) they are greyish white


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## JayPetro

Pretty sure that's just limestone


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## xriddler

Hi guys, I picked up some rocks from my backyard and was wondering if these rocks are safe to use for an aquarium. Can anyone help identify if any might be harmful?


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## getochkn

I've used backyard rocks before.



















Some rock will raise your params slightly like pH or gH, etc but unless you're keeping delicate fish or shrimp, they'll adjust to whatever the rocks leech into the water but that's usually limestone, sereyi stone, etc. Those should be fine.

Give them a good cleaning. 20:1 bleech solution soak in very hot water, then rinse well, over dose on prime to get rid of any bleach and should be good. Don't boil rocks, they can do explode if trapped air is inside them, etc.

I've also went got some big chunks of lava rock and then got a bag of small BBQ lava rock from Canadian Tire for your BBQ and used them for small accent pieces.


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## John_C

*Love it!*

I love this post!!! More informative than most aquarium books I've read !


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## jimmyjam

nice stickey. I think my rock that I took from a local left over contractor schene is def leaching into my tank. I have never seen melting of plants like this in my 20 years of aquascaping.


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## Jamblor

If you can take a close up pic I can try to tell you what it is.


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## woody4000

Hello, I was wondering if anyone knows what type this rock is?. Can I use this type of rock in my tank? I was told it may be landscaping "river rock".. I did the vinegar test and there was no fuzzing. Any help would be great. Thank you.


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## Jamblor

woody4000 said:


> Hello, I was wondering if anyone knows what type this rock is?. Can I use this type of rock in my tank? I was told it may be landscaping "river rock".. I did the vinegar test and there was no fuzzing. Any help would be great. Thank you.


River rock could mean anything.

My first guess was a marble, but since you said it doesn't fizz it could be a quartzite.

I would try to scratch a bit of the surface of the rock so there is a bit of powder and try the vinegar again if you really want to make sure.


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## woody4000

Do you think it could be Rhyolite? The only thing I can find online that looks like it. http://geology.com/rocks/rhyolite.shtml

Once again thanks.


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## Jamblor

It's possible. Usually rhyolite has scattered crystal that are larger than the ground mass of the rock. If it is rhyolite you should see either quartz (clear, shiny) about 1-3mm in size. Or hornblende (black, thin, rectangular) about 1-3mm long.

If you don't see any of those larger crystals on the surface then it probably isn't a rhyolite. Also, I've found that rhyolite isn't quite common from local shops I've seen in the GTA.


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## woody4000

Here is another picture with the inside visible. I chipped off some of the rock and added vinegar and still no fizzle. I believe you are right that's its Quartzite. I did put it into the sun and there was a sparkle all over the inside of the rock. Not sure if that helps.


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## homerjay

woody4000 said:


> Here is another picture with the inside visible. I chipped off some of the rock and added vinegar and still no fizzle. I believe you are right that's its Quartzite. I did put it into the sun and there was a sparkle all over the inside of the rock. Not sure if that helps.


I too believe it is Quartzite. I compared your picture to a specimen in my collection and although it is difficult to 100% distinguish by a picture I would say that's what it is. This is totally fine to put in your tank should you want to.


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## Jamblor

woody4000 said:


> Here is another picture with the inside visible. I chipped off some of the rock and added vinegar and still no fizzle. I believe you are right that's its Quartzite. I did put it into the sun and there was a sparkle all over the inside of the rock. Not sure if that helps.


That close up picture reveals a very characteristic texture of quartzite, therefore I'm confident to say it is quartzite. And I'll bet on it too 

Enjoy!


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## qualityshrimpz

great post! i am going to refer to this in the next cpl days setting up my tanks at my new house, thanks!


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## PACMAN

you ROCK Jamblor!


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## risingl3gend

What do you guys think about buying slate from a landscape company? If you clean it real good and do the vinaegar test before you put it in the tank. Bcs you can get all kinds of sizes and variations for a very good price. Will the slates from there work or will they be unsafe?


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## lastlid

*Hi Jamblor*

Hi Jamblor,

There are a couple of your rock sample photos in this thread that I would quite like to use. Would that be okay.

Interesting that you guys do the vinegar test for limestone.

Lastlid.


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## lastlid

risingl3gend said:


> What do you guys think about buying slate from a landscape company? If you clean it real good and do the vinaegar test before you put it in the tank. Bcs you can get all kinds of sizes and variations for a very good price. Will the slates from there work or will they be unsafe?


I think, that if it is slate, it should not respond to the vinegar test.

Shale can look a bit like slate and it could give a positive reaction to vinegar, depending on the type of shale. Shale can be calcareous.

We have a lot of slate around here where I live. But I am in the UK.


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## Jamblor

lastlid said:


> Hi Jamblor,
> 
> There are a couple of your rock sample photos in this thread that I would quite like to use. Would that be okay.
> 
> Interesting that you guys do the vinegar test for limestone.
> 
> Lastlid.


Sure thing


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## restoredvd

Do you guys know what type of rock these are?


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## tom g

*wow*

all these years and I have never seen this thread ,very cool


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