Quartz Species Part 5

Hi everyone,

Today I would like to finish up the macrocrystalline family.  I would like to say that it has been very interesting to learn all the neat things about quartz so far.  I have enjoyed the journey so far and I hope you have too.  Today I am going to discuss Quartz cat's-eye, Hawk's eye and Tiger's eye.  Very earthy and animalistic today!  Please join me on my journey and I hope you have fun and learn new and exciting things today.  So let's being the learning!  As before I am using the information found in the book Gemstones of the World by Walter Schumann as the basis for all the information I am using in this blog.

So let's talk Cat's eye quartz.   The colour for cat's eye quartz is white, grey, green, yellow, and brown.  The colour streak is white and the Mohs hardness is 7.  The density is 2.58-2.64 and there is no cleavage.  The Crystal system is trigonal, usually massive and the crystal composition is silicon dioxide.  The transparency is semi-transparent to translucent.  The quartz cat's eye has numerous fiber-like inclusions of rutile create an effect called chatoyancy.  Chatoyancy is the description for the play of light on the surface which shows the effect of  cat or bird or animal of prey. This type of quartz can be sensitive to some acids.  These quartz can be found in Sri Lanka, Brazil and India.  When the stones are cut as a cabochon it shows the chatoyancy like a cat's eye which is cause for the name.  When someone calls a stone cat's eye without the quartz name attached to it most people then take the stone to mean the chrysoberyl  version of the cat's eye.

Hawk's eye is finely fibrous opaque aggregate that is formed when quartz replaces the mineral crocidolite.  The colours range from blue-grey to blue-green and iridescence of planes and fractures have a silky luster.  This type of quartz is also sensitive to some acids.  This stone is used primarily for ornamental objects and costume jewellery.  Cabochons are cut to show the chatoyancy, which is reminiscent of the bird of prey's eye.

Tiger's eye is formed from Hawk's eye where the iron from the decomposed crocidolite has oxidized to a brown colour.  The luster is silky on the fractures.  This type of quartz shows chatoyancy stripes, because the structural fractures are crooked or bent.  Tiger's eye quartz is usually found in South America, Australia, Burma, India, Namibia and the United States.  This type of quartz is used for necklaces, costume jewellery and objets d'art.  The cat's eye appearance happens when the cabochon is cut to show that effect.

I hope everyone had fun today.  I really enjoy learning new things and I hope you do too.  Please let me know what you think of this or any other posted blog.  I would love to hear back from you so please drop me a line to let me know what you think.  Until next time.

The rare gem lady