Rag and Bone,
if you have found pyrite, it is a very good indication of gold present. it would be processed as a by product, but gold no less. whenever you find minerals such as calaverite, krennerite, sylvanite, quartz and pyrite, it is a very good indication. just remember, gold is not always the buttery yellow people envision in their minds. depending on the associative minerals and gangue, gold can be tinged red, black, green, silver, brown, reddish brown, etc. gold now adays is processed as a by product of coper, silver and lead ores. with the occaisional open pit, large heap, cyanide leach, micron gold processing. about three percent nationwide, comes from placer deposits.
when you're out and about, look for copper ores and their associative minerals and scheelite (tungsten) sperrylite (platinum) iridosmine (osmium) but, be careful if you do come across iridosmine, it is poisonous. worse than large doses of arsenic. it is the osmium content that makes it unstable.
it will more than likely be found in grains and flakes in your black sands.
osmium being the heaviest mineral. SG of 22.5.
according to my copy of a range guide to mines and minerals, looks like you are in copper country. excellent opportunity for specimen hunting on the old tailings piles.
if you are looking to understand and identify what you are looking for, i suggest finding and reading a copy of De Re Metallica, by georgious agricola, written in 1557. they have reprinted copies translated into english that wont cost more than twenty or thirty bucks.
it is definitely a good read.
hope that helps a little,
Ezra