GOLD QUARTZ-VEINING, ... What to 'LOOK' for !
MANGANESE-OXIDE minerals (Steel-Grey Colour) associated with the Iron-oxide 'dirty' Quartz-Veining.
YES, this is a VERY good 'appearance / association' that MANY gold-bearing quartz veins have.
YES, sometimes there is MORE Mn-Oxide & Fe-Oxide minerals than actual Quartz in the vein. This is because MANY gold bearing quartz veins have had a 2nd generation of fluids re-introduced into them that are often rich in all the Iron-oxide and associated minerals that Gold loves..... so don't JUST look for quartz veins.... the 'Ugly' (sexy) Quartz-Veining is often the BEST !!! 
BRECCIATED Quartz-Veining (veins that have 'broken-up' bits of Quartz all through it) are the very common types that have gold.... VERY good to be able to notice / look out for.
YES, this mineral can often make the quartz vein 'softer' and more susceptible to weather/decompose faster than the surrounding quartz veins that have no gold. So keep a close look at the quartz veins by CRACKING them open with your pick.
