Mineral 3
Specimen dimensions: 3 x 1⅜ x 2⅛ inches (77x35x53 mm)
Specimen weight: 11 ¾ ounces (335 grams)
Collection: Highland Campus
For reference: the U.S. penny is 0.75 inches [19.05 mm] in diameter.
Distinguishing Properties (click this to reveal) - make your list of observations before peeking
Distinguishing Physical Properties:
The first thing that you might observe is that this mineral is light, or whited Colored. This is possibly a clue, but this mineral can be found in a wide array of colors and shades.
The next thing that you might observe is that this mineral looks like a box that's leaning or has been pushed over. It's crystal faces are not quite at right angle sides, opposite sides are parallel, but one face intersects with the other at about 60 and 120 degrees. This is called "Rhombahedral Cleavage".
Hardness isn't something you can see, but you can scratch the back of your fingernail with this mineral, and if you tried you could scratch this mineral with a nail.
Finally, if you think that you have a specimen of calcite, the definitive test is to squeeze a small drop of acid or strong vinegar onto the surface, and if you observe vigorous bubbling (these are carbon dioxide, or CO2 bubbles), then you have a specimen that contains Calcium, and it is probably calcite.