Identification Help Needed

I found this today while out looking for rocks in a creek near our home.  It was on a creek that doesn't cross a road upstream and is surrounded by farm fields.  I live in northwest Missouri about 50 miles north of Kansas City.   When I first saw it, I figured it was a piece of glass or chalcedony.   However, when I got it home and cleaned it up, I realized it was extremely lightweight.  After looking on the internet we kind of narrowed it down to plastic, copal, or amber.   We have a lot of glacial material here from up north but I didn't find any amber locations in Canada that would have made sense with the way the glaciers moved but I didn't look into this extensively.   Anyway, we started doing various tests which are noted below.  

The first photo is holding the rock up to the sun.  It really grabs the sun.   The inside looks extremely clear.  I don't see any insects or plant material but I will take another look tomorrow when I can look at it in the sunlight.  The second photo shows a fractured? surface.  Note the micro fractures on this surface.  Also, where the light is reflecting you can see an indentation which to me looks like it might have been a bubble.   I didn't see any other bubbles on the inside.  The rock has what looks like conchoidal fractures but not as distinct as you see with glass or agates.   The third photo shows a rough side of the rock.  The rock is 2 inches long from tip to tip and about an inch thick in the thickest places.  


Specific gravity.  Keep in mind I was doing this with a kitchen scale and beaker that has 25 ml graduations.   I weighed it twice and got sg of .94 and 1.42.   Regardless of what it actually is, it is light.   It would sink quickly in fresh water.   I did the salt water test (7 tsp of salt in one cup water).  It sank but not very fast.  My impression was that it wasn't too far from floating.  What I read was that amber will float.  

Hardness.  My fingernail wouldn't scratch it but a copper penny did scratch the surface so it is in the right range for amber or copal.  

Chipping.  I read on one site that cutting with a scalpel (I used small exacto knife) and producing chips means amber and producing a peal means copal.  It produced small chips.  

Static Test.  I rubbed the rock in a dish cloth for 60 seconds and was able to pick up and hold a small piece of paper about 3/16 square.  But barely.   

Hot pin test.   I tried doing this but not sure how hot to get the pin.  I held it on our ceramic top stove under highest setting for 20 to 30 seconds.   It barely made an indentation in the material.   I couldn't smell anything.   Does someone know how hot to get the pin?   Does it need to be red hot?  

So plastic, copal, amber or something else?  Please give me your thoughts.  Are there other tests?  I did read about acetone but was a little afraid to do this.  Thanks.