Ways to determine gold include:
1. Compare its weight to a similar host rock of the same size. A VERY noticeable weight difference will get you excited, but will not be definitive.
2. Specific Gravity Test, but you have to know precisely what the host rock is.
3. The Scratch Test - scratch the "gold" areas and see if the scratches and caused by brittleness or deformation. Silicates are brittle (including Pyrites) providing chips and dust, whereas gold is ductile and will only deform.
4. Measure conductivity with an ohmmeter (this is my favourite). Put both probe tips on the same target grain without touching each other and if you get a reading of a few ohms or less, then get very excited. Try on other grains. Sometimes these grains are connected within the host material. This would be gold.
5. Crush and Pan. This will destroy a potentially valuable specimen, but is a definitive test.
6. The final test is really for the experienced and careful. Etch with a dilute (5%) concentration of Hydroflouric Acid (HF) for a few days to 1 week. This will dissolve ironstone, silicates (Mafic and Felsic) etc, but will not touch the gold. Be VERY careful with using and neutralising/disposing of this acid. Use proper body protection! Use only Nitrile gloves!