how would you know if it's a gold you found underground?

Answer 1

The gold that is mined underground is not found in the nuggets that you see being pulled out of streams or out of shallow soil. The gold that is mined from underground is an ore, mixed in with other materials and which is locked inside the rocks. When they mine the ore, they crush the rock, and then treat it with chemicals that extract the gold by leaching it out. There are veins of ore that were deposited by hydrothermal activity, and these veins are often associated with quartz. The minerals deposited in these veins were extracted by hot water as it seeped through the rock material. When this mineral rich water reached a break in the rock fabric, it would accumulate and possibly even flow. As it did so, it would deposit its mineral cargo into these fractures, forming a mineral vein. As more of the mineral rich water entered the vein, the minerals that were already there, deposited on the rock surface, created centers of growth for mineral crystals. Because of the crystal structure of individual minerals, the molecules of minerals that are being held in the water are attracted to other molecules of the same shape. This is how you get large beautiful quartz, calcite, pyrite, and other crystals to “grow” in a vein. This is also how the gold is gathered and deposited in the vein. The prospector that is looking for a place to mine gold would look for an ore or mineral vein and see if it contained traces of visible gold. If it did, then he knew the gold came from the rocks around the vein. He knew not all the gold was extracted out of the rock by the hot water that deposited the stuff in the vein, so if he mined out the rock and crushed it, he could extract the gold that was still there.

The gold nuggets that you think of as being found in streams, or within a few feet of the surface on dry ground, is formed after the gold is released from the parent rock due to weathering. The gold dust, which is heavier than most of the other materials weathered out of the rock, is carried down with the water that helps erode the rocks. When the gold dust gathers in the streams, it settles in the low areas. Because gold is soft and malleable, when it collects in these low spots, it is pressed and formed together into flakes. When a spring flood or heavy flow runs through the stream, these pieces of gold are dislodged and moved down stream where they settle into another low place, with other pieces of gold. Given enough time, these pieces will press together and eventually form a nugget.
Most of the gold you find in streams when you pan is in the form of dust or flakes.

A good way to test the material in you pan to tell if it is gold or pyrite is:

Gold is heavier than pyrite so put a little water in your pan and give it a gentle swirl; if the material flows rapidly with the water, it is pyrite. If it stays stationary or is reluctant to move, it is gold.

Gold is softer than pyrite so if you have a flake of material press on it with your fingernail, gold will bend, pyrite will break.

Gold has a luster even in the shade; pyrite shines in the sunlight. Put your hand over the pan creating a shadow; bring the shadow over the material. As the shadow moves over the material, gold will still have a luster; pyrite will turn dull in appearance.

If you want to learn more or are interested in actually doing some panning or prospecting, look up the "Gold Prospectors Association of America (GPAA)". They have a magazine that gives lots of good information and stories from prospectors. If you join, they have a large book full of sights and claims you can go to, many for free.

Answer 2

Contrary to what sherqta says, gold is one of the native elements and its compounds are rather rare. Gold cannot be identified with certainty in field. It has certain diagnostic properties which can lead one to suspect it to be gold. Unfortunately, it occurs in a wide variety of rocks, particularly very old (Archaean) rocks and has several associated elements/minerals like arsenic, sulphides, tungsten, iron, smoky/bluish quartz etc. It is very heavy, but you cannot weigh a gold flake in field. It is shining yellow (barring coated golds) - but so is some sulphide minerals like pyrite or chalcopyrite. It forms amalgam with mercury and also dissolves in aqua regia (1:3 mixture of conc sulphuric acid and nitric acid) - but both are hazardous processes and I do not recommend them. One possible way out is to grind the whole material (your suspected flakes + host rock) and pan them to separate out the heavies - but again you need an expert panner for that.
Considering all, I should say the best way for you is to collect the sample, powder it to - 200 ASTM size and take it to the Geology Department of the nearest university to analyse it.

Answer 3

Gold is found mostly associated with a quartz reef. The difference between gold and fool's gold(Pyrite) can easily be identified by rubbing to get streak.Pyrite gives black or greyish black streak on rubbing the surface but gold does not give black or greayish streak.

Answer 4

Normally gold is found in association with other mineral, most of the time as compound. Native gold is rare, specifically in depth (under ground).

Answer 5

Gold is yellow and soft, iron pyrites, (fool's gold) is yellow, hard and brittle. Pyrite will burn when heated, releasing sulphur dioxide (coff coff) but gold remains unchanged.

Answer 6

Vey heavy, shines when you clean it off, and tests positive for gold using a jeweler's test kit.