Using Acid to Treat a Chain Coral Fossil 

I wish I could take credit for that. I got the idea from a book. I think it was the Lake Huron Rock Picker's Guide.

It did, didn't it? I'm really happy with it.

Sometimes I'm funny without meaning to be. Other times it's intentional.

I’m glad you like it. It’s not hard to do yourself, just be careful with the acid.

You're welcome!

I'm not sure why it doesn't. It's a fun thing to try.

Yeah I would have thought it would just disintegrate too. Or I'd walk about five steps and I'd drop it 🤣

You're welcome. That rock is still setting out on the counter in my shop.

I’m much less careful when I’m not on camera. I thought I should set a good example.

@@MichiganRocks I think it's a good idea too. One tiny, tiny splash of that muriatic acid would destroy someone's sight, wouldn't it?

@@nancygaxiola5412 I wear goggles when I use it. I just don't wear most of the other stuff.

I think I could have dumped the acid in much quicker with no problem.

You're welcome, Marilyn.

That's what I'm here for!

Be careful!

Cool idea, but it wouldn’t be strong enough. You could do that if you left out the acid and polished it instead.

​@@MichiganRocks oh! there should be the way to stabilize coral somehow. I agree that polished slab would look great but I was captured with the idea to get rid of calcite and get that mystic labyrinth

They’re pretty rare around here, but this is where I found all of them. I’m pretty excited whenever I find one.

I hate when my wife watches my videos when I’m in the room because I have to listen to my voice.

They're not all that rare. I don't find many, but I'm sure on some other beaches they're more common.

@@MichiganRocks Oh, You're in Michigan. Then you will understand. I was in Wisconsin up by Washington Island. They must just be in that area.

I've got some more ready to go in, possibly later today if the weather clears up.

Don’t worry, I don’t have any moon rocks.

I get a lot of comments about the sound of the waves in my beach videos. I don’t get many bird sound comments, but I agree, they are great too. I can hear loons flying to and from a small lake near here. I also love the sound of geese and sandhill cranes flying over. We have turkeys in the yard, and of course all the little tweety birds.

Michigan Rocks I’m from Kalamazoo Michigan lower south west and I recognize the sounds of the birds is similar lol #puremichigan The Best state in America minerals climate all season Breath of Fresh Air not to mention Fresh water #rockhound for life 💯

I do too!

I know that some people use vinegar, but it takes a lot longer. Given enough time and vinegar, I think you might possibly achieve the same results. I saw no downside to getting it done quickly, other than the possibility of severely burning yourself with acid, that is.

Definitely not an indoor project. What do I do with it? So far is setting where I took the picture of it. I’m afraid to move it. It should probably be mounted on a board and out under glass.

You’re welcome!

I never thought about serving it with milk. Crunchy!

G Libby this is fossilized coral from about 350 million years ago. I’m not sure what it’s made of at this point, but it’s not calcium. As you said, the acid would have reacted with that right away.

Isn’t the chain coral a silica replacement? That is why it is harder and impervious to the muratic acid.

@@rebeccagoldberg8333 That sure makes sense. I suspected that was the case, but I've never actually studied up on it. Thanks!

No, it works on calcite based rocks. It might work on some other minerals, but that's one I know for sure. I have done it one time on some mine rock from the U.P. to remove calcite from a piece of copper ore. More copper was exposed, but there was another type of matrix that it didn't remove.

No problem. I need to go play with acid again one of these days. I have some other fossils I want to try.

I soaked another one part way, so that the coral sticks out the top an eighth inch or so and is still solid below that. It's much more durable, but still looks cool.

You'll need to go to at least two different lakes to find those. Superior is best for agates and Michigan and Huron on good for Petoskey Stones and puddingstones. I know of a lot of beaches that I could recommend, but could you narrow down the area you're thinking about visiting?

@@MichiganRocks I am staying in Mackinaw City, but am thinking about Munising, Leland, I will drive anywhere within 2.5 to 3 hours from mackinaw city. I have family in Newberry so will be going there as well.

I thought it was really cool. I want to try it with some other types of coral. I know there's at least one other one that this works for. I can't remember the name of the coral though.

Thanks!

I've heard of people using it on Petoskey Stones, but I have never understood why. It's just going to eat away everything like you said. I've polished a lot of Petoskeys and have never used acid in the process.

I think so. I tried it with a couple other fossils, but they just dissolved uniformly.

I don't have much expensive equipment. I started this hobby about 7 years ago, and I have been slowly accumulating mostly used equipment since then. The flat lap in this video cost me $45. Of course the discs and things that go with it wear out and cost money too. I have four saws, the most expensive one cost $400, but those don't come along very often. My most expensive thing is my homemade tumbler. If you're patient and watch Craig's list and talk to people, you'll run into some deals eventually. My favorite trim saw was given to me when we bought some furniture. The store owner was delivering a chair to our house and heard my rock saw in the garage. He offered me a saw that he hadn't used in years. I spent $150 getting it running.

Quartz doesn’t dissolve in acid, so it depends if the matrix is quartz.

She blinded me with science!

This is the only coral I’ve tried it on. I would think that most would completely dissolve, but it would be interesting to try it on some others.

Oh, I heard you should neutralize as long as you used the acid, to stop it from continuing to dry it out.

I think my flat lap is homemade, but I didn’t make it. Sorry I can’t help you out.

Nothing says “Happy Indepenence Day” like soaking a rock in acid!

Muriatic acid. You can buy it at someplace like Home Depot for about $8 a gallon.

@@MichiganRocks Thank you Rob and Happy thanksgiving to you and your family Carl Zatsick

Yes, I tried to make a video last summer of some others that I thought might work. They dissolved more or less uniformly so there wasn't anything to see in the end. I had a really good intro to that video too.

I find a few in Lake Huron, but they're pretty rare. I think there are more in Lake Michigan, but I'm not sure which beach to recommend.

@@MichiganRocks Oh nice, i live very near lake michigan, havent seen much aside from crinoids though haha. I'll keep my eyes out

Yeah, that was a bummer. This one is still in one piece though.

No, I think the whole thing would dissolve.

@@MichiganRocks i figured as much. i was unable to find a single even remotely successful attempt online. hoping to get back up north in the fall for some chain coral to try it on. revealing the actual fossil sounds like a lot of fun to me.

Muriatic. You can buy it cheap at a hardware store. It's used for cleaning mortar off of bricks, among other things.

It sounds like you're talking about waste water in general, not about water I used to dissolve the matrix rock with acid in this video. I have a three bucket system dealing with waste water. All water from my tumblers goes into a bucket. Don't pour it down the drain, or it will harden like concrete and block your pipes. I let the bucket settle as much as it will, leaving still cloudy water on top. I siphon the top part with the most clear water into another bucket and then either dump it in the gravel at the side of the road or into a hole in the woods behind my house. The "hole" is actually a pretty nice hole. I built a wooden box out of some old treated lumber that goes down about two feet. There's a trap door on top to keep someone from accidentally falling in. Where I live the soil is mostly sand, so the water drains out pretty well. It rarely gets much ice down in the hole even in the middle of winter. The only problem is that eventually the small rock particles in the dirty water clog the sand and it doesn't drain anymore. I can dig out the bottom for a while, but eventually I have to move the box to a new hole. I have only moved it once in about 8 years though, so it's not too bad. My water often contains borax which I use in the Lot-O tumbler. Borax acts as a herbicide, so you don't want to dump it on your lawn. What's left in the buckets after siphoning off the top is left to dry out and then it goes in the trash.

@@MichiganRocks thanks for the info. Protecting the environment here in Traverse city and anywhere I choose to move in my lifetime is important especially with the chemicals, elements, materials.. Lapidary uses. There's a Lapidary class here in TC that I should check out and get involved with to make sure I'm disposing of the waste properly.

@@happyisthealero I don't think that rock dust is bad for the environment. Borax is the only thing you have to be a little careful with just because it can kill plants if you put it right on them. Borax is used as a laundry additive, so it goes out into septic drained fields all the time. It's fine if it's under grass for example, you just don't want to put it on top.

Muriatic.

I don't feel that the subjects of my videos really go out of style too quickly, so feel free to watch as many older ones as you would like to. I hunt Lake Huron a lot more than Lake Michigan, so most of my chain corals are from Huron. I only find a couple per summer, so they're pretty rare here. I believe Lake Michigan has more of them them, but I couldn't tell you which beaches have the most. As with most rock hunting, the more remote beaches will probably be better to hunt just because they're so much less picked over. The last one I found was a small one at Point Betsie Lighthouse, although that spot is heavily hunted.

I used the brush on kind of polyurethane. I would be worried about overspray if I used the spray stuff. As the acid and limestone react, they both get used up. If you had a lot of acid and a small amount of limestone, you could dissolve more limestone. If you had a lot of limestone and just a little acid, you wouldn't dissolve all of the limestone. All of this is irrelevant though, because a gallon of muriatic acid costs about $8 at Home Depot.

Ok, thanks! I love watching your videos! Keep up the good work!!

Oh, one more thing... what was the baking soda/water ratio you used? 😊

@@brendalittle528 I didn’t measure anything. It’s like the acid ratio. As long as you have enough baking soda, the small amount of acid left on the wet stone will be used up in the reaction before the baking soda. Just use more that you think you’ll need and it will neutralize the acid.

I haven't used vinegar. I think it works like muriatic acid, but a lot slower (and safer).

I didn't read the concentrations on the bottles. The first jug was from a hot tub store, but had been in my garage for about ten years. I don't think it would get old, but I don't really know. Anyhow, I ran out and went to Home Depot to get another gallon of it. I think this one was marketed for cleaning up grout from brick. I'm not sure if it's more concentrated or not. It worked well whatever it was.

@@MichiganRocks ah ok

I think I read about coating with polyurethane in a book or on the internet. I'm not so sure that it's necessary. I do like that I ground the bottom flat first because that gives it something to rest on without being wobbly. I just used a tiny hobby paint brush and painted on a coat or maybe two of polyurethane. The resulting fossil is very, very fragile. Soaking it in polyurethane sounds like a good idea to me.

@@MichiganRocks What made you decide on a 10:1 ration of water to acid.....would a 4:1 ratio speed up the process or more likely destroy the coral? Or is that just a standard used when mixing Muriatic Acid and water? Just a safety tip reminder for anyone reading this - make yourself aware through the many internet sources on the safe handling of Muriatic Acid. Wear appropriate gloves (not the ones your grandmother knit you), where a proper face mask - like a respirator (you don't want the fumes getting into your lungs) and when mixing add the acid to water and not the other way around (Never add water to acid, as an exothermic reaction will occur, propelling the acid out of the container and onto you.). One other question - seeing that you weren't jostling the chain coral piece you had around - is there any reason why you couldn't do 2, 3 or 4 pieces at a time if you had enough room for all of them? Thanks again Rob - you've spurred my interest in giving this a shot in the next week or so.

@@scrand6 I didn't measure anything. I ended up adding acid faster as things progressed. I'd just check for bubbles every now and then and when the bubbles stopped, I'd pour in a more acid. You'll get the feel for it as you go. I get the feeling that adding acid a little at a time or a lot at a time didn't matter much, it just lasted longer if I added more. I don't see any reason why you couldn't do several at once, but I'd suggest doing one at a time until you get the hang of it.

I found it in the northeast part of the lower peninsula of Michigan. The matrix rock is limestone or calcite, I think. Most of the fossils here are limestone, which is why acid dissolves it. I'm not sure what the coral part is.

Hi Landon!