A common and useful test is to see if the sample reacts with diluted hydrochloric acid.  To do the test you will need 10 percent hydrochloric acid.  Most hardware stores will sell "Muriatic acid" which is diluted hydrochloric acid.  The muriatic acid my local hardware store had was 20 percent hydrochloric acid, so I just needed to dilute it one to one with water.  It is helpful if you have a dropper bottle to keep it in.  I found these on Amazon.

To test the sample, place a few drops on a specimen.  If you immediately see a reaction with bubbles you have an indication the mineral is a carbonate and the most common and most reactive is calcite.  

It should be noted that some carbonate minerals will only react if the specimen is powdered first.  This is true for dolomite.  An easy way to do this is to use an unglazed porcelain plate that is used for streak test and apply the acid to the streak.

A few myths

1. It is DANGEROUS!!  You will often hear people say not to use hydrochloric acid because it is too dangerous.  You do not want to get 10 percent hydrochloric acid in your eyes nor your tongue but getting it on your skin is normally not an issue.  Just wipe it off or rinse it off.  If you are concerned or have very delicate skin, purchase disposable nitrile gloves from the hardware store or auto store.  .....Back in the 80's when I was the mineral lab TA, often someone would think the hyalite sample was calcite and put acid on it and then someone down the line would lick it.  

2. It will destroy your specimen!!  If you have a very delicate sample, most physical tests may damage it, but a few drops of diluted hydrochloric acid are not going to damage most samples.  The bottom image is of the calcite after the acid was applied to it.  No damage.

3. Use vinegar instead!!  It is safer!!  While vinegar is safe it also does not reactive.  You normally have to submerge the sample in vinegar to see the reaction or place a few drops on the specimen and wait 10-15 minutes and use a magnifying glass to see if you see bubbles.  

Side note......

If you are in the Mammoth Cave National Park area, you can hit me up and I normally have spares I'm happy to give out.  Feel free to reach out to me at my contact.

Thank you

 Thank you to the following people for reviewing this article:

Mark Gottlieb

Debbie Joplin