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Techniques for Collectorsextracting limonite crystals from rock
27th Jun 2017 15:46 UTCDaniel Bennett
27th Jun 2017 16:11 UTCReiner Mielke Expert
27th Jun 2017 16:12 UTCKevin Conroy Manager
I would definitely recommend getting a rock trimmer if you're going to be working on a lot of delicate specimens, or if you want more control over where the rock breaks.
27th Jun 2017 16:19 UTCBob Harman
In Indiana this is often seen as iron rich (ferroan) dolomite corrodes into the amorphus limonite mass. After soaking, I use a hi pressure cleaning gun to help remove this stuff.
CHEERS.......BOB
27th Jun 2017 16:51 UTCTed Hadley
27th Jun 2017 17:47 UTCDon Saathoff Expert
It seems that we are not sure what you are talking about. As Bob said limonite is a mixture of iron oxides/hydroxides and tends to form as a product of the weathering or "breakdown" of another iron mineral. If your crystals are cubes, the limonite has probably replaced pyrite. If they are pyramidal it has replaced magnetite or chalcopyrite or, again, pyrite - or any of many iron minerals. If you could add a clear picture of the specimen we would have a better understanding of what you are dealing with and would be more likely able to help.
Don S.
27th Jun 2017 18:17 UTCMatt Courville
Daniel, I would try practicing trimming on junk rocks more than temperature techniques, other than buying a rock trimmer. Acid only works with particular things such as garnet, epidote, in calcite etc. Some use saws to trim-down, but many don't like this and feel that it makes the piece loose value. If you don't mind, this could also be an option at a local club if you don't care to buy them yourself.
27th Jun 2017 19:01 UTCWayne Corwin
28th Jun 2017 01:59 UTCDaniel Bennett
these next two pictures are one piece that I'm done hitting with a hammer.the crystals might be attached to each other.
I glued the corner back on.
I have a pile of broken rock that might have more crystals inside if I had a way to dissolve the rock. how to speed up the natural process of breaking it down.
28th Jun 2017 02:15 UTCDaniel Bennett
this one would pop right out but I wont.
28th Jun 2017 05:00 UTCGregg Little 🌟
28th Jun 2017 06:02 UTCDaniel Bennett
I might trim 736 flat on one side so it will stand and display the crystal. what can be done with 744?
28th Jun 2017 06:06 UTCDavid Sheumack
28th Jun 2017 10:27 UTCPeter Nancarrow 🌟 Expert
I would say that the rock matrix doesn't look like the sort of material which would be susceptible to any sort of "heat and chill" technique, which wouldn't be just as likely to fracture the crystals as well, so some sort of mechanical/hydraulic splitting, using something like this:
would probably be the most sucessful way of extracting them.
Having said that, if they were mine, I would keep them with at least some attached matrix (such in your last photo), which has much more geological/mineralogical interest than simply a stand-alone oxidised pyrite crystal.
Pete N.
28th Jun 2017 15:33 UTCDoug Schonewald
The only way to break open the rock and expose crystals is a splitting tool or a hammer and chisel. Using an electric drill with a small carbide bit, and drilling a line of holes, can enable you to break the matrix away exactly where you want it. You are going to lose some crystals, so collect more than you need. Once you break the rock enough to partially expose a crystal you could try an electric engraving tool and use that to carefully chip around the crystals and clean up the drill marks. Another option is a small dremel tool with diamond tools to grind and cut away the matrix to better expose the crystals. I've seen some pretty nice work done with a small trim saw and then chipping away the saw marks with an engraving pencil. The result was a nearly invisible cut line and a fine specimen. It is very time consuming and labor intensive, and may not be worth it commercially, but it will give you some very nice specimens for your personal collection or to give as gifts to friends.
Doug
28th Jun 2017 17:45 UTCScott Rider
If you are trying to sell them, then leave 736 alone. It may sell better being on a matrix. People like that, as it can make displaying it easier, and its more interesting to really serious collectors whom are more interested in pieces on matrix than being loose.
29th Jun 2017 19:21 UTCDaniel Bennett
here is an after picture of 744/745.
it looks like it was a single crystal that broke. any guesses on when this occurred? at the time of rock formation or later on during some seismic event?
this is the engraver.
thanks so much for the good responses.
29th Jun 2017 19:41 UTCDaniel Bennett
I also want to show how cool they look on there own. with no work. these were loose in the gravel.
a before and after using the engraver
thanks again
29th Jun 2017 20:10 UTCMatt Courville
29th Jun 2017 23:54 UTCScott Rider
However, I would do the tests on damaged, ugly ones if you have any first, just in case it doesn't turn out the way you wanted.
10th Mar 2019 00:37 UTCEd McKay
10th Mar 2019 01:54 UTCKevin Conroy Manager
13th Mar 2019 00:47 UTCEd McKay
13th Mar 2019 00:50 UTCDoug Daniels
13th Mar 2019 23:32 UTCEd McKay
17th Mar 2019 21:49 UTCEd McKay
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Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2024, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: March 29, 2024 14:47:21