Interesting. I am going to collect some black sand soon. I will try to replicate.

Woody,
The black sand is probably hematite. This will affect the streak. It should be a reddy purple. Which is what you are getting when you are grinding it down.
Check out Hematite/ironstone/ magnetite on Wikipedia. This may help your identification.
Let me know if you get stumped. I'll get out the old geology textbooks and lend you a hand.
Cheers
James

Bluestix, there are many types of black sand. Unless you live in the same area it is unlikely you may be dealing with the same mineral.
Cheers
James

Thanks James that helps a lot. My assumption at first was that it was plain old magnetite, however after I observed that it turned dark red I figured there was something else going on. After reading up a bit on hematite at your suggestion I am more convinced that hematite is indeed what I have. Although after reading about other related minerals I am also thinking that Goethite might also be present. I base that on the fact that the area I am retrieving the sand from is surrounded by lots of iron oxides of various types, and it's found in a dry wash bed. Basically my understanding of the mineral is that it is formed by the weathering of other iron oxides, it can also be precipitated out of ground water or other sedimentary conditions. Also the color is right and it is often found with hematite. One of Goethites modern uses is as an earth clay pigment, and when I ground this stuff up my mortar and pestle was permanently stained the dark red color. I don't have alot of background in geology or anything though so I'm curious to hear your thoughts on that analysis.
Thanks for the reply and the suggestion.
-Woody

Woody,
I wouldn't be confident of the presence of goethite.
If it is it would be in small quantities as it is a hydrated form of iron. The key is that the streak of goethite is yellow, not red.
Lepidocrocite has an orange streak which is a posibility or you could cover it under the term Limonite which is generally considered to be a mix of cryptocrystaline goethite or lepidocrocite along with absorbed water.
Simply speaking it is a field term to describe hydrated oxides of iron with poorly crystaline characters whose real identity is not known.
I would go with Hematite with small amounts of Lepidocrocite in the absence of a sample/ pictures and tests such as specific gravity, streak hardness etc.
Sorry it has taken so long to follow up, but that's what you get when your a father of 4!
Can send you some scans of my mineralogy handbook if that helps
James

Hello all,

Whether the jar should be full to the top of acid (mixed with water), or is it enough just to cover the rock?
And the rod need to be from magnetic iron?
Vlado

Well sorry for the late reply here, what I have done is filled the jar up all the way because what you want to happen is for the acid to digest the important materials in the rock, and that just takes time. Also iron is a magnetic material so while it does not have a magnetic field of its own it is attracted to magnets. Just make sure that the iron rod is pointing toward the north. Then leave it alone for a few weeks/months, the actual time will vary depending on what kind of material you are processing and how much acid you have in the container. Hope this answers your question, happy experimenting

Thanks James, sorry its taken me so long to get back here, I have been busily at work reading rock hounding guides and picking up gem and mineral handbooks and running around collecting rocks. My first run with the acid has taken nearly 5 months so far partially because I had the first jar going in the garage which is not heated and seeing as how it had been freezing at night it greatly hindered the process, so once I figured out what was happening I moved it to a not-often-frequented area in the house and it has done much better. Anyways when I actually start getting to the firing stage I'll try posting more results.

Thanks for reply Woody,

It helps, just wonder if i fill the jar up all the way, whether it dissolve iron rod ?

No problem. I filled mine all the way up and I actually just harvested material from the first rod I set up. And while there was not much left of the rod where the material was growing it definitely works to deposit material on the rod. I also noticed that the material that is deposited on the rod is soft just like John says in the video. I will try and keep posting updates as I progress.
Oh and when you do get to the harvesting stage make sure you let the rod dry for a few days as it takes quite a while. I kind of rushed things this first go around and soft wet materials are not easy to grind up in a mortar and pestle. Also if anyone else is working on this it might be nice to see what other people's findings are in this fascinating area of study.
Cheers
- Woody

Is it normal that the bottom of the rod which lies on the rock-slightly dissolved already. Is it a problem if the ratio of acid is a little higher ?
Thanks

What happened? No updates?

Woody Jr, you say you are using rocks... what type of rocks are they?

Sorry for the delays in replies here.
Vlado: That seems to be normal, at least for what I have seen, although a 9:1 ratio of water to acid seems to also be the best starting place. I can't remember what that comes out to be in terms of percentage, but I know that it's right around 3-5% HCL. I made a 10% concentration in one instance and it doesn't seem like it has changed much, but that's not to say that it won't come out later as being something significant. I think personally the best thing would be to start with what John B specifies. 9:1 water:acid ratio, iron rod pointed to the north and bide the time while nature does its work.

EndTime:
The rocks I'm using at the moment are some rocks I've picked out of an old gold mine from where I live. The composition tends to be a mixture of quartz and pyrite. I picked up a bunch of magnetite out of a wash that runs by my house using a magnet. I also picked up some chalcedony near my house. I found a particular type of rock that was very dark purple and had slight magnetic properties. I can't remember the name of it right off the top of my head. I'm also using pyrite. Really anything I can get my hands on that looks interesting. In order to get an idea of what to look for I did some research on geology, rock formation and specifically how to identify certain minerals. From there it's how you get those materials and harvest them that makes the end result. Interestingly enough, things like chalcedony, quartz, and a lot of opals all have the same chemical composition, they just have different molecular crystalline structures. Anyways hope that answered a few questions anyways. As I get more data I'll try and update with results and such.

Hi again,
I tried the whole process with the iron pyrite and iron rod pointed to the north. After approx two month, botom of the rod was disolved but nothing of material for harvesting.
Where is the mistake ?
I used this kind of pyrite