Expert: Joe Norris - 6/28/2009

Question
My son lives in a rural part of connecticut.  He and my grandsons have found rocks, soil,etc. that they feel contain precious minerals.  Is there a way that these can be analyzed to see if they have any value.

Answer
For me to even make an attempt at telling you what kind of rocks that you have, you need to do a few things for me.  Because you found the rocks in Connecticut the location is useless unless the rocks were in place since many of the surface rocks are not in their original position. If they were in place I need to know that location; if they were not in place I need to know the general location.

1) I need several pictures of the rock; taken from different angles.

2) I need to know the hardness of the rock.  Hardness of a rock is based on what mineral/rock type will scratch another mineral/rock type.  Since you don't have ten different minerals, that make up the scale, you can use some artificial harnesses from common things.  The scale goes from 1 to 10 with talc = 1 and diamond = 10, but you can use common things to determine hardness.  Your fingernail =~ 2; penny =~ 3; knife blade = 5.5.  Scratch your rock/rocks and tell me what its hardness is.  

3) I need to know the streak of the rock.  The streak is the color of the rock when the rock is scratched by porcelain.  If you can find a piece of porcelain and scratch the rock on the porcelain the color that shows up on the porcelain is the streak.  If you have or can find a piece of porcelain, fine, but if you can't you might want to get what is called a streak plate; they are in-expensive and particularly if you like rocks in-valuable in determining rock types.  

4) The last thing that I need to know and you may or may not be able to do this - is the specific gravity.  The specific gravity of a rock is its weight relative to volume.  The standard is water which has a specific gravity of one.  The way that you determine the specific gravity, without a jolly balance (a machine used for this purpose), is somewhat complicated.  You need to find a beaker (graduated in metric) large enough to contain the rock.  Fill the beaker with enough water to cover the rock.  Take a measurement of the water level.  Add the rock and take another measurement of the water level.  Subtract one from the other; which gives you the quantity of water displaced.  Determine the weight of the displaced water.  Divide the smaller number of the two into the larger of the two.  This will give you the specific gravity of the rock.  

Let me know I can probably tell what class of rock that you have.