Monday, 14 November 2011

Turquoise ~

Turquoise is a soft mineral and needs to be treated with care.  It's porous and prone to discolouration even from contact with the skin.  When I was considering buying turquoise I specifically asked that it be untreated, but the gem retailer assured me that all good quality commercial turquoise is lacquered - in order to protect the surface.  Without this anything worn against the skin could be expected to rapidly discolour, first to green and then to a nondescript brown.  

I decided to accept the constraint and bought the one pictured below.  The other two necklaces in the picture are azurite-malachite in the centre, and around the outside, calcite or aragonite.  (The jury is still out on this one!)

In the enlargement below you can see that the beads contain small flecks and that the colour varies.  Flecks in turquoise are likely to be pyrite, and any spidery veining, limonite.

The last paragraph of the Wikipedia article linked to above includes this excellent advice about the care of turquoise jewellery: 
Being a phosphate mineral, turquoise is inherently fragile and sensitive to solvents; perfume and other cosmetics will attack the finish and may alter the colour of turquoise gems, as will skin oils, as will most commercial jewellery cleaning fluids. Prolonged exposure to direct sunlight may also discolour or dehydrate turquoise. Care should therefore be taken when wearing such jewels: cosmetics, including sunscreen and hair spray, should be applied before putting on turquoise jewellery, and they should not be worn to a beach or other sun-bathed environment. After use, turquoise should be gently cleaned with a soft cloth to avoid a build up of residue, and should be stored in its own container to avoid scratching by harder gems. Turquoise can also be adversely affected if stored in an airtight container.
Turquoise pebbles
Turquoise is often faked through the use of a variety of different materials and methods.  If you are in one of the cheaper gift shops or even gem shops you may see strings of beads which look like turquoise, but are actually dyed howlite.  This practice is relatively common.  Howlite in its natural state is white, or close to it.  I have written about this stone separately - refer link.

Turquoise is classed as a phosphate mineral.

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