|Mojave Nugget, a gold nugget weighing 156 ounces (4.9 kg). |
From the Stringer district, Kern County, California.
Gold - my precious!
Pure gold (Old English gulth "bright", ghol "yellow", Sanskrit jval "shaining") has an attractive bright yellow color and luster which it maintains without oxidizing in air or water. It is a chemical element with the symbol Au (from Latin aurum) and atomic number 79 which makes it one of the higher atomic number elements which occur naturally.
Gold is one of the least reactive chemical elements solid under standard conditions. The metal therefore occurs often in free elemental (native) form, as nuggets or grains in rocks, in veins and in alluvial deposits. Less commonly, it occurs in minerals as gold compounds, usually with tellurium.
Like all elements with atomic numbers larger than iron, gold is thought to have been formed from a supernova nucleosynthesis process. Their explosions scattered metal-containing dusts (including heavy elements like gold) into the region of space in which they later condensed into our solar system and the Earth. Because the Earth was molten when it was just formed, almost all of the gold present on Earth sank into the core.
Where to look for gold on Earth?
- Gold is found in ores in rock formed from the Precambrian time onward.It most often occurs as a native metal, typically in a metal solid solution with silver.
- Most of the gold that is present today in the Earth's crust and mantle was delivered to Earth by asteroid impacts during the late heavy bombardment.
- Native gold occurs as very small to microscopic particles embedded in rock, often together with quartz or sulfide minerals such as "Fool's Gold", which is a pyrite.
- The metal in a native state is also found in the form of free flakes, grains or larger nuggets that have been eroded from rocks and end up in alluvial deposits called placer deposits.
- Microbes can sometimes play an important role in forming gold deposits, transporting and precipitating gold to form grains and nuggets that collect in alluvial deposits.
- The world's oceans contain gold. Measured concentrations of gold in the Atlantic and Northeast Pacific are 50–150 fmol/L or 10–30 parts per quadrillion (about 10–30 g/km3).
From Widipedia, text heavily rearranged by me.
Read the original article from here.