The Opal or Tourmaline are the Birthstones for October. 

The opal is a fragile gemstone cut as a cabachon. The opal can have a white, grey or black colour.  Black being the rarest.  The opal has a wide range of internal colours this is caused by internal diffraction. The opal hardness ranges between 5.5-6.5.  Tourmaline is commonly known as green but tourmaline can come in all the colours, most common being green and pink.  Tourmaline hardness is between 7.0-7.5.

The Opal is said to increase imagination and dreams.  Tourmalines are used to strengthen the body and spirit with green balancing males and pink balancing females.

Opal is also the 14th anniversary gemstone.

Tourmaline is also the 8th anniversary gemstone.