Mercury is the only naturally occurring liquid metal at room temperature. Since it lacks a crystal structure, mercury is technically not a mineral but is a “mineraloid”. It was named after the planet Mercury, which was named after the Roman god of travel. Another popular name for this mineral is quicksilver; derived from the Greek words hydros, meaning water and argyos, meaning silver (because this silver mineral occurs at room temperature as a liquid).
Mercury was known to a number of ancient civilizations. It was known to the ancient Chinese and Hundus civilizations, and was found in Egyptian tombs which date from 1500 BC. It was used by the ancient Greeks as an ointment, and by the Romans as a cosmetic. By as early as 500 BC mercury was already used to make amalgams with other metals.
Some interesting properties:
Mercury freezes at -39°C and when it solidifies it crystallizes in the isometric crystal system. It is a very good conductor of electricity, though it is a poor conductor of heat. Finally, mercury has a specific gravity of 13.5 and up. This means that it is a very dense metal.
The demand for mercury has declined in recent years because of new technologies and environmental laws. Some past and present uses include:
- Mineral specimen for collectors
- To manufacture chlorine and caustic soda
- Conducts electricity so it is useful in electronics and electrical applications
- Necessary in fluorescent light tubes
- Was an important ingredient in batteries, but newer types of batteries use other metals
- Scientific instruments such as thermometers and barometers
- Combined with other metals and used for fillings in teeth
Mercury is rare in its native state. It occurs as very small blobs on top of mercury ore minerals, never in “pools”. The tiny blobs can be found in small crevices/pores and stick to their host mineral. The blobs do not fall off or roll around, but stay attached in position unless tampered with. The main mercury ores include cinnabar and calomel, though there are a few other secondary minerals. Areas which are known to have mercury ore include:
- Almaden, Spain
- Idrja, Former Yugoslavia
- California, Oregon, Texas and Arkansas, USA
The demand for mercury has declined in recent years. Not a lot of mining is currently being done. Some of the demand has been met by the recycling of mercury from obsolete or worn out machines, scientific apparatus, and batteries. It is also recovered as a by-product from gold mining operations in the United States.
Ingested mercury mixtures are hazardous and can even be lethal if a large amount is ingested. Mercury should never be heated as its vapour can also be deadly if inhaled. The vapour is a neurotoxin, which can cause nervousness, trembling, personality changes, and in extreme cases, can even cause dementia.
Fish are less susceptible to mercury poisoning and can consume greater amounts than that of humans. The mercury accumulates as you travel up the aquatic food chain. This means that fish can be a source of mercury poisoning in humans.