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As can be seen in the chart below, the high specific gravity (relative density) of gold as compared to other minerals with which it may be found forms the basis for all gravity methods of separating the gold, including panning, sluicing, dry washing, gold wheels, etc. Specific gravity is a relative density, the ratio between the weight of a substance and the weight of an equal volume of water at 4° C. Below is a list of many common minerals, including those most commonly found associated with gold, along with their specific gravity and hardness. Notice that gold has one of the highest specific gravities and many common minerals that may be found in the field are much lower. As can be seen in the table below, minerals which might be confused with gold such as pyrite, chalcopyrite and mica also have much lower specific gravity. Mica, which forms in sheets, will try to float out of the gold pan. Mercury is listed because the old timers used mercury in separating the gold, losing some in the streams as a consequence. The mercury will be amalgamated with gold and should be kept (being very careful as mercury is toxic). |
| Another distinguishing property of gold is its malleability. Gold will flatten when struck while pyrite and chalcopyrite, both being brittle and harder than gold, will shatter. As a guide for hardness, the fingernail is a little over 2, a copper penny (not the newer zinc pennies) about 3, a steel knife just over 5, glass about 5.5 and a good steel file about 6.5. |
| The following table is based on data from the "Manual of Mineralogy", 19th Edition by Cornelius S. Hurlbut, Jr. and Cornelis Klein, John Wiley & Sons, Inc. 1977. |
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|
| Name |
Specific Gravity |
Hardness |
| Arsenopyrite |
6-6.2 |
5.5-6 |
| Calcite |
2.7 |
2.5-3 |
| Chalcopyrite |
4.1-4.3 |
3.5-4 |
| Chromite |
4.6 |
5.5 |
| Cinnabar |
8.10 |
2.5 |
| Copper |
8.9 |
2.5-3 |
| Epidote |
3.3-3.6 |
6-7 |
| Feldspar |
2.4-2.8 |
5.5-6.5 |
| Galena |
7.4-7.6 |
2.5 |
| Garnet |
3.5-4.3 |
6.5-7.5 |
| Gold |
15.6 - (19.3 pure)
|
2.5-3 |
| Hematite |
4.9-5.3 |
5-6.5 |
| Ilemenite |
4.5-4.7 |
5-6 |
| Lead |
11.3 |
1-2 |
| Limonite |
2.7-4.3 |
4-5.5 |
| Magnetite |
4.9-5.2 |
5.5-6.5 |
| Marcasite |
4.89 |
6-6.5 |
| Mercury |
13.6 |
liquid |
| Mica |
2.7-3.4 |
2-3 |
| Monazite |
4.6-5.4 |
5-5.5 |
| Olivine |
3.2-4.3 |
6.5-7 |
| Platinum |
14-19 |
4-4.5 |
| Pyrite |
4.9-5.2 |
6-6.5 |
| Pyroxene |
3.2-3.9 |
5-7 |
| Quartz |
2.65 |
7 |
| Rutile |
4.2-4.3 |
6-6.5 |
| Scheelite |
5.9-6.1 |
4.5-5 |
| Silver |
10-12 (10.5 pure) |
2.5-3 |
| Tourmaline |
3.0-3.25 |
7-7.5 |
| Wolframite |
7.0-7.5 |
4-4.5 |
| Zircon |
4.6-4.7 |
7.5 |
|
| Name |
Specific Gravity |
Hardness |
| Gold |
15.6 - (19.3 pure) |
2.5-3 |
| Platinum |
14-19 |
4-4.5 |
| Mercury |
13.6 |
liquid |
| Lead |
11.3 |
1-2 |
| Silver |
10-12 (10.5 pure) |
2.5-3 |
| Copper |
8.9 |
2.5-3 |
| Cinnabar |
8.10 |
2.5 |
| Galena |
7.4-7.6 |
2.5 |
| Wolframite |
7.0-7.5 |
4-4.5 |
| Arsenopyrite |
6-6.2 |
5.5-6 |
| Scheelite |
5.9-6.1 |
4.5-5 |
| Monazite |
4.6-5.4 |
5-5.5 |
| Hematite |
4.9-5.3 |
5-6.5 |
| Magnetite |
4.9-5.2 |
5.5-6.5 |
| Pyrite |
4.9-5.2 |
6-6.5 |
| Marcasite |
4.89 |
6-6.5 |
| Zircon |
4.6-4.7 |
7.5 |
| Ilemenite |
4.5-4.7 |
5-6 |
| Chromite |
4.6 |
5.5 |
| Rutile |
4.2-4.3 |
6-6.5 |
| Chalcopyrite |
4.1-4.3 |
3.5-4 |
| Garnet |
3.5-4.3 |
6.5-7.5 |
| Olivine |
3.2-4.3 |
6.5-7 |
| Limonite |
2.7-4.3 |
4-5.5 |
| Pyroxene |
3.2-3.9 |
5-7 |
| Epidote |
3.3-3.6 |
6-7 |
| Mica |
2.7-3.4 |
2-3 |
| Tourmaline |
3.0-3.25 |
7-7.5 |
| Feldspar |
2.4-2.8 |
5.5-6.5 |
| Calcite |
2.7 |
2.5-3 |
| Quartz |
2.65 |
7 |
|
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| Gold in the pure state has a specific gravity of 19.3 but the presence of other metals results in the range of values above. Most gold contains about 10% of other metals, silver being the most common, resulting in a specific gravity of slightly over 18. For example one source gives an average of 18.6 for the quartz gold of California. Another source states that gold from the Weaver placers in Arizona has a specific gravity of 18.53. |
| Lead is included above to show that it has a fairly high specific gravity, especially as compared to the minerals found in black sand and other common minerals. This is why lead shot, used in hunting, or lead fishing split shot is used in gold panning practice. Being very soft it can also be easily flattened or pounded into various shapes to mimic small nuggets. However due to the toxic problems with lead, it will probably end up being banned for hunting and fishing. |
| From BLM Technical Bulletin 4, Placer Examination Principles and Practice, the heavy minerals found in black sands consist of the following minerals in order of frequency: magnetite, ilmenite, garnet, zircon, hematite, chromite, epidote, olivine, limonite, rutile, pyroxene, monazite and the Platinum group metals (Platinum, Palladium, Iridium, Osmium and Rhodium). Of course this will vary by area. Bureau of Mines publication, Information Circular 8517, by J.M. West gives a slightly different list of black sand minerals which includes magnetite (magnetic iron oxide), ilmenite (iron-titanium oxide), hematite (nonmagnetic iron oxide), marcasite (an iron sulfide), rutile (titanium oxide), scheelite (calcium tungstate), wolframite (iron, manganese tungstate), tourmaline (boron and aluminum silicate), zircon (zirconium silicate), chromite (iron and chromium oxides), and cinnabar (mercury sulfide). |