Argentite facts for kids
Argentite is a mineral made of silver and sulfur. Its chemical formula is Ag2S. The name comes from the Latin word argentum, which means silver. It is a very important ore, meaning it is mined to produce silver metal.
Argentite is unique because it only truly exists at high temperatures. When it cools down, its internal structure changes, turning it into a different mineral called acanthite. Because of this, scientists at the International Mineralogical Association do not consider argentite to be a separate mineral species anymore. However, the name is still used to describe the cubic shape that the mineral often keeps even after it has cooled.
Contents
Understanding Argentite
The Temperature Trick
Argentite forms in the cubic crystal system, which means its atoms are arranged in a cube shape. However, this structure is only stable when the mineral is very hot—specifically, above temperatures of about 173 °C (343 °F) to 179 °C (354 °F).
When the mineral cools down to ordinary room temperatures, the atoms inside shift. It turns into a monoclinic crystal structure, which is the structure of the mineral acanthite. Even though the inside changes, the outside shape often stays the same. It still looks like a cube or an octahedron (a shape with eight faces).
In geology, this is called a pseudomorph. A pseudomorph happens when a mineral changes its internal makeup but keeps its original external shape. So, most specimens labeled as "argentite" in museums are actually acanthite that has kept the shape of the original argentite.
Physical Characteristics
Argentite (or the acanthite pseudomorph) has distinct features that help geologists identify it:
- Color: It is usually a blackish lead-grey color.
- Luster: It has a metallic shine, but it can look dull if it has been exposed to air for a long time.
- Hardness: It is quite soft. On the Mohs scale of mineral hardness, it scores a 2.5.
- Sectility: The mineral is sectile, which means it can be cut smoothly with a knife, almost like lead.
- Weight: It is very heavy for its size, with a specific gravity of 7.2 to 7.4.
History and Mining
Where is it Found?
Argentite is found in mineral veins, often mixed with other silver minerals. It belongs to the galena group of minerals. When it is found in large amounts, it is a valuable source of silver.
Some of the most famous places for finding this mineral include:
- Mexico, where large masses have been discovered.
- The Comstock Lode in Nevada, USA, which was a major silver mining area in the 1800s.
- Jalpa, Zacatecas, in Mexico, where a related copper-rich mineral called jalpaite is found.
Naming the Mineral
The mineral has been known for a long time. It was mentioned in 1529 by the scholar G. Agricola. However, the name argentite was not officially used until 1845, when it was named by W. Haidinger.
Before it was called argentite, miners and scientists used other names for it, such as:
- Glaserz
- Silver-glance
- Vitreous silver
