Re: Is there a map that would explain where in Australia gemstones are found?

This is a very general question, and more one for a bit of library research than for an expert 
scientist. However, here is an answer, of sorts:

Yes, there is undoubtedly such a map. There are a number of books about Australian gems. They 
are mostly called things like "A Field Guide to Australian Gems and Minerals". (I do not know if that 
is an actual title, but it embraces most of the keywords). Here is a good one:

Author         Talent, John A.  
Title             Minerals, rocks and gems : a handbook for Australia. 
Published     [Milton, Q.] : Jacaranda, [1970].

You will notice that it is rather an old one. You will not find it in the bookshops. If you are in 
Australia it is quite likely to be in your local library, or they will be able to find something similar 
for you. It might not be too easy to locate elsewhere in the world (I drew a big blank on Amazon, 
but I am not the most skilled library searcher!)

Gemstones are found nearly everywhere in Australia. Anywhere that is not a gemstone field has 
probably just not been prospected! (That is not quite true, but...)

You can sometimes get a clue from place names: just to the South-East of Melbourne there are two 
towns quite close together called "Emerald" and "Gembrook"; in the North-Eastern Suburbs we 
have "Diamond Creek". There is also an "Emerald" in Queensland, quite close to smaller towns 
called "Sapphire" and "Rubyvale". Two opal fields in different parts of North-Western New South 
Wales are called "White Cliffs" and "Lightning Ridge". In North-Eastern Victoria we have "Eldorado" 
(Aussies mostly do not speak Spanish, so it has been condensed into a single word).