1.... that coral reefs are the largest structures ever built on planet Earth by any animal including man

2.... that a pearl has a life expectancy of only 100 years, or 150 at the most

3.... that one ounce of gold can be beaten or flattened into a sheet of 100 square feet, or drawn into a wire almost a mile long, or made into a foil that is less than five millionths of an inch thick and virtually transparent

4.... that your turquoise ring could change its colour if you wash your hands without removing it and even become smelly if you immerse it in dishwater or oily liquid

5.... that two flints or a flint and steel will strike a spark that can be used to start a fire, but also that two quartz stones will serve the same purpose

6.... that some gem materials come from strange sources.  One is grown on trees (amber- formally tree sap). Some start as an irritant inside the shell of a mollusc (pearls) or grow in the mouths of animals (ivory).  One begins as an "apartment complex" for a colony of sea creatures (coral).  One comes from volcanoes and is the product of stone so hot that it melts (obsidian). One is even thought to be formed of rock which has melted after being hit by a meteorite falling from outer space

7.... that what determines the hardness graduation of lead pencils, which, by the way, range from 9H (hard) to 9B (extra soft) is achieved through the addition of varying amounts of clay to the graphite.  Graphite is the 'lead' in lead pencils

8.... that when held in your hand up to your ear, sulphur sizzles and pops.  This is caused by cracking inside due to the expansion caused by the heat of the hand

9.... the the polishing agent known as "jewellers rouge" is made of powdered hematite