Here is a water-clear tabular quartz crystal from Brazil.  It is only 1.5" thick at its thinnest, and has grown in a tabular ("tabby") formation, so-called because its flat shape resembles a thin tablet. On this amazing piece, which I have heard called a "potato chip" crystal for obvious reasons, the two flat sides dominate, though the other 4 sides are present, though quite small.  And, the crystal is double terminated.  There is one curved section that I thought was broken, but on close examination there is no damage.  There are also two dark gray spots which were caused by exposure to background radiation.  This is a very rare and unusual form of quartz, a habit that I have only seen once before.