SUPPORT US. If mindat.org is important to you, click here to donate to our Fall 2019 fundraiser!
Log InRegister
Home PageAbout MindatThe Mindat ManualHistory of MindatCopyright StatusWho We AreContact UsAdvertise on Mindat
Donate to MindatCorporate SponsorshipSponsor a PageSponsored PagesMindat AdvertisersAdvertise on Mindat
Learning CenterWhat is a mineral?The most common minerals on earthInformation for EducatorsMindat ArticlesThe ElementsBooks & Magazines
Minerals by PropertiesMinerals by ChemistryAdvanced Locality SearchRandom MineralRandom LocalitySearch by minIDLocalities Near MeSearch ArticlesSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
Keyword(s):
 
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
Mining CompaniesStatisticsUsersMineral MuseumsMineral Shows & EventsThe Mindat DirectoryDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day GalleryMineral Photography

Etching Iron Meteorites on the Kitchen Table

Last Updated: 1st Aug 2019

By Gareth Evans

Etching Iron Meteorites on the Kitchen Table

The meteorite shown in the accompanying photos was prepared for etching by first deep cleaning using the electrolysis process described in a previous article (see How to Clean Rusty Meteorite - a practical approach). The total cleaning time in this instance was about 3 weeks.

03074800015646977988176.jpg
970537
09393620015646977997250.jpg
970539


After it had been cleaned it was sliced in half using a bimetallic blade on the kitchen table. It took about 30 minutes of intermittent sawing with the bimetal blade to cut it in half.

06968530015646978015466.jpg
970540


The cutting was easy and occurred without incident. This was expected since both Iron and Nickle are much ‘softer’ than the saw blade. In the event of a carbide nodule being present I did have a 1mm diameter diamond wire saw ready. The mitre saw shown in the photo was a cheap $20 import from the local hardware store.

After sawing the slices were polished flat on a granite surface plate using progressively finer grit silicon carbide paper. I started with 120-grit and finished with 3000-grit. When the surface of the slices had a mirror-like luster they were cleaned with dry ethanol and then etched.

05032610015646978032477.jpg
970542
02784430015646978055892.jpg
970543
06795300015646978065092.jpg
970545


Initially I used Nitol, which is a solution of concentrated nitric acid (1 ml) in ethanol (99 ml). I was not happy with the result. The Nitol did not give a deep etch, so I used Ferric Chloride. Ferric Chloride is used to dissolve unprotected copper in circuit board design, and I use it for this purpose when I have no Ammonium persulphate on hand.

The first observation is obvious. You spent three weeks removing chlorides and now you expose the meteorite to chlorides. And this is true, but the exposure time is only two minutes not 500 years, and after etching, the meteorite is left in a 10% solution of sodium hydroxide overnight.

As my dear departed mother (Born Polesworth UK, 1906) would often say, proof of the pudding is in the eating. And the meteorite still shows no sign of rust, and it was etched nearly eight years ago.

The big advantage of Ferric chloride is the end result. It produces sharper Widmanstätten lines with substantially more contrast, and the kamacite plates show stronger Neumann lines than that observed with Nitol. From a practical perspective Ferric Chloride is much easier to purchase than concentrated Nitric acid. You simply brush a light layer of solution on the polished surface and the etching occurs within seconds of exposure to the solution.

09825650015646978075158.jpg
970544
07179300015646978098742.jpg
970546


What I hope to show is that you do not need a lot of equipment to achieve first class results. With the sweat of your brow and the power of your muscles, you can add value to many ordinary things.

So when you see a ‘nasty’ meteorite, buy it and turn it into a thing of beauty.





Article has been viewed at least 784 times.

Discuss this Article

7th Aug 2019 22:24 BSTAlfredo Petrov Manager

Thanks, Gareth.
Very useful!

I wonder whether ferric sulphate could work the same way?
(Just wondering because ferric sulphate minerals are abundantly available (hundreds of Kg) at a mine I collected at. I‘ll give it a try just for fun.)

7th Aug 2019 23:18 BSTGareth Evans

There are many etchants that can be used. If you look online under the general heading of macro etchants for revealing internal crystalline structure of metals you will find many, many recipes. I toyed around with a few when I was preparing my periodic displays. 

Will ferric sulphate work, perhaps - in chemistry there is a lot of 'suck-it-and-see' work.

I used Ferric chloride because it is easy to get, and I used it a lot as a young boy when I was making printed circuit boards at home. I wanted to suggest chemicals that would be easy to get. And this is becoming a problem as our societies become more of a nanny state. 
 
Mineral and/or Locality  
Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization. Public Relations by Blytheweigh.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2019, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: August 25, 2019 05:46:35
Go to top of page