| 3-letter term for the rocks mined for aluminum, iron or lead among others |
ore |
100 |
May 23, 1988 |
| Of a stalagmite, a stalactite or a helictite, the one that only grows from the ground up |
stalagmite |
200 |
May 23, 1988 |
| Pyrite contains both sulfur & iron but only a "fool" thinks it contains this |
gold |
300 |
May 23, 1988 |
| From Greek for "to write", it's what does the writing in most pencils |
graphite |
400 |
May 23, 1988 |
| The hardness of a mineral is measured by this scale |
Mohs |
500 |
May 23, 1988 |
| Youâll discover not gold, but a black mark, after rubbing this âgoldâ on porcelain |
foolâs gold |
100 |
April 22, 1986 |
| A scratch test wonât reveal a mineralâs allergies, but this property |
hardness |
200 |
April 22, 1986 |