New York in the late 1880's to 1890's saw some prospecting in about 11 counties. I don't have a NY map handy but from Herkimer east, south along the Hudson and one county in the south west along the PA border. (Herkimer, Sarotoga, Hamilton, Washington, Allegany(?), Dutchess) There is a mining report at the public library in Watertown that is from that period. It is rather long and if I remember correct they would copy the report for about $38, long report. The best area is around Scanandaga Lake, Route 29 and a faultline that runs northeast along the lake. West of the lake are some interestinly named areas. Gold Hill, Miners....... can't remember and more. Most of the gold was in a sand layer about 20-25 feet deep. There may also be deposits that moved down down from Canada during the last ice age.
There is not much available for mining/prospecting laws in NY. Keep a low profile and tell everyone your looking for garnets. Which bty are also north of Scanandaga Lake.
There are also reports of nuggets found on the shore of Lake Bonaparte near Ft. Drum. There are also quartz deposits in Jefferson County near Antwerp. I used to know where there were 2 old smokestacks that you could only see in the spring from lead mines in that area.
There is also a "story" of an Indian that used to find silver somewhere in the Adirondaks that he melted for bullets. No, it wasn't Tonto!