Tektites are an amazing type of natural glass formed by the heat and impact of meteorites landing on Earth, 15 million years ago!  Debris was thrown high into the air, meaning that Tektites often display a characteristic 'droplet' shape as they cooled whilst falling.    Though usually black in colour, a variety of Tektites known as Moldavite are unique in their olive-green colouring and can only be found in a small area surrounding the river Moldau in The Czech Republic/Germany.   Treasured for centuries by various cultures, Tektites have been used for many purposes - from arrowheads to lucky talismans.  Gram-for-gram, Tektites are rarer than diamonds, as only 50 tonnes were ever formed on earth (compared to over 26 tonnes of diamond produced PER YEAR!)