How to Clean Mineral Specimens
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How to Clean Mineral Specimens

This describes the methods used to remove stains and other soil causing conditions from mineral specimens. This article also describes some of the chemicals used in the process of cleaning.

Not many mineral specimens straight from the field look as good when they are on display. Getting them ready for exhibition takes a lot of knowledge, and more then a slight amount of good old fashioned elbow grease. Minerals that have come right from the field are apt to have various stains and can be covered with lichens. These all have to be removed before you can exhibit any of these mineral specimens. One of the most important steps in cleaning mineral specimens is to try the technique being used on a small sample first to get a feel on how the cleaning process will work before using it on larger specimens.

Unless the specimen is too delicate the first step is to clean it using dish washing detergent and a tooth brush. This step can be used on most mineral specimens as a method of removing the initial grime that is usually found on minerals fresh from a field environment.

The most common staining found on minerals is iron oxide or if you prefer “rust.” Iron oxide stains on minerals can be removed using oxalic acid (OA), a naturally occurring acid that can be bought at your local hardware store. OA can also be found in many fruits and vegetables, two of the most common sources are rhubarb leaves or spinach. The OA dissolves the iron oxide stains leaving the mineral clean.

In this age of the heightened awareness of terrorism it may be difficult of impossible to buy oxalic acid, but you can make your own as it is found in many plants. One of the best sources is tea. Other plants with especially high concentrations of OA include sour grass, buckwheat. You can extract OA by steeping the plant in hot water allowing the OA to be dissolved in solution.

After the surface dirt on the specimen has been removed by brushing place the specimen put it into a plastic container covering it with a solution of OA and leaving it there until the iron oxide stains are completely dissolved by the action of OA. Remove the specimen from the OA and wash it thoroughly with running water. Put the specimen back into a plastic container covered with fresh water that is frequently changed for an additional three days to completely remove any lingering remains of the OA.

Another difficult thing to remove from mineral specimens are lichens. They can be removed using household ammonia or bleach. This is also used by placing the specimen into a plastic container and covering it with a 5% solution of the desired chemical. Don’t mix ammonia and bleach together because this releases a poisonous gas in the form of chlorine. This was used in WW I as a weapon of mass destruction.

Calcium carbonate is another substance that quite often has to be removed from specimens. The most effective cleaner for this is a 5 – 10% solution of hydrochloric acid also known a muriatic acid available from masons supply stores. This is also used by soaking the specimen in the solution then repeating the washing and rinsing steps undertaken with OA.

If in doubt about the use of any of these chemicals it is best to consult with an expert. The author will assume no responsibility for the use of these chemicals; you do so at your own risk.

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Comments (3)


Excellent and well explained topic.Thanks

Good read. Well done.