Silver

Authors: Maria Grimaldo, Tara Williams, William Dunlap

Name: Silver

Chemical Composition: Ag

Color: Can either be light gray to silver or white to black.

Streak: Light gray to silver

Hardness: 2.5 - 3

Cleavage/Fracture: Silver has hackly fracture (4). Hackly fracture is also called jagged fracture because when the mineral breaks, the surface becomes jagged and sharp (11). Silver is relatively soft, but does not break at specific weak points that would be associated with cleavage.

Crystal Form: Silver has an isometric crystal system meaning the crystals form with three axes that are all identical and 90° from each other (12). Silver rarely forms in environments that allow the mineral to create the ideal isometric shapes and, instead, tends to form between rocks in long smooth wiry strands, tree-like patterns known as dendetric, or flat, flaky plates (2).

Luster: Metallic

Special Features: Silver is ductile and malleable meaning it can be molded and formed. Silver also transmits electricity better than any other metal (3).

Varieties: The different varieties of silver are Native Silver, Antimonial or Antinomian Silver, Aresenian Silver, Auriferous Silver, Chilenite, Kongsbergite, and Küstelite. Native Silver contains no other elements but silver (1). Antimonial or Antinomian Silver icontains, at most, 5% Antimony. Arsenian Silver can contain up to 7% Arsenic. Auriferous Silver contains less than 10% Gold. Chilenite silver is a variety that is bismuth-bearing (4). Kongsbergite is Silver that contains about 5% Mercury. Küstelite is a variety of Silver that contains 10% - 30% gold (4).

Mineral Group: Silver belongs to the Native Elements (2). The Native Elements group is comprised of 3 subgroups that include; metallic, semi-metallic, and the non-metallic elements. Silver is in the metallic sub-group because it has a metallic luster, is a good conductor of electricity, and it is malleable and ductile.

Environment: Silver usually forms in areas that have hydrothermal activity with calcite (5). When hydrothermal veins cool down, boil, or have a chemical reaction between the impure water and the rocks lining fissures the veins are located in, it can cause precipitation of silver and other minerals. Another way silver is formed is through volcanogenic massive sulfides. This process is when seawater meets the magma-heated rocks under the ocean and there is a reaction between the two creating a solution. This solution can rapidly cool and leave behind mineral deposits that can contain silver (10).

Associated Rock types: Silver is most commonly found in silver ore (2). It is also commonly found in volcanic basalt rocks (1). Silver can also be found in the veins of granite, clay slate, mica schist, limestone, and in the ores of copper, iron, and zinc (7).

Occurence in North America: Silver isn’t found in huge abundances in the United States, but several mines in Alaska, Colorado, Nevada, and Michigan large amounts of silver have been found (3). Several mines in Ontario, Canada contain an abundance of silver as well (1).

Economic Uses: Silver is most commonly sold in the form of sterling silver, which is 92.5% silver and 7.5% other metals, usually copper (8). Sterling silver is utilized because silver is too soft in its pure form. One of the most popular uses for sterling silver is jewelry. It is desirable for jewelry because it is less expensive than gold and people do not have allergic reactions to silver like they do with comparative metals, like nickel. Sterling silver is also commonly used in silverware and other tableware (8).

Silver is also formed into coins and used as currency. This is no longer a common practice in the United States. Before the Coinage Act of 1965, all half-dollars, quarters, and dimes were made of 90% silver; after the Coinage Act half-dollars contained 80% silver while quarters and dimes contained none (9). Collectors now buy and sell silver coins at prices often larger than their face value. Usually older coins are valued higher than newer coins.

Industrial Uses: Silver is one of the three most common precious metals after gold and copper. Its mined in ores where it is always mixed with other minerals such as lead and zinc. The ores are mined often from open pit mines and as the ore is removed it is crushed into smaller pieces. Mercury is then added to extract a thin layer of silver. More than 75 % of the silver recovered or mined is from residue of other extractions (10). Silver is most commonly used industrially for its electrical properties. Out of all the elements, silver is the number one conductor of electricity and is commonly used industrially in electrical circuits (1). In 2003, 1230 metric tons of silver were made into wires and put into electronic gadgets. Some examples include; light poles, refrigerators, and batteries (8). Silver is also used as a photoactive chemical for developing film (4). When silver is combined with oxygen and nitrogen is creates silver nitrate which turns black when exposed to light (8).

First Notable Identification: Around 2500 BC, the first granulation of silver alloy was found in the Middle East (6). Since it was discovered, people have used it mainly for decoration and trade because it is such a soft, malleable metal (6). The word silver comes from an Old English word "seolfor" (4). The first documented use of the word silver dates back to 1478 (4). The ancient Romans used the word argentum which is why the chemical abbreviation is Ag (4).

How We Identified It: You can identify silver through its color, as it has a noticeable, bright white color when it hasn’t been tarnished. A hardness test is also helpful during identification as it won’t be able to scratch a copper penny, and it also won’t have any cleavage.

Don’t Confuse It With: Platinum because silver is softer than platinum, which has a hardness of about 4.5. Silver also tarnishes while platinum does not and the two minerals do not usually have the same crystal form. Galena can also be confused for silver, but it is much darker than silver and has a darker streak. Molybdenite is another similar mineral, but is softer than silver with a hardness of about 2 and does not have the same crystal form (1). Also, lead can sometimes look like silver, but it is much softer than silver with a hardness of about 1.5 and when it oxidizes it turns a bluish-green color (1).

Bibliography:

1. The Mineral Silver. (2019). In Minerals.net. Retrieved from https://www.minerals.net/mineral/silver.aspx

2. King, Ph.D., RPG, H. M. (2019). Silver. In Geoscience News and Information. Retrieved from https://geology.com/minerals/silver.shtml

3. Newton, D. E. (2010). Silver. In K. J. Edgar (Ed.), Chemical Elements (2nd ed., Vol. 3, pp. 539-544). Detroit, MI: UXL. Retrieved from http://link.galegroup.com/apps/doc/CX3012400095/GVRL?u=oregon_chemeke&sid=GVRL&xid=87289feb

4. Silver. (n.d.). In mindat.org. Retrieved from https://www.mindat.org/min-3664.html

5. Mineral description : Silver. (1998, March 7). Retrieved from http://www.geology.neab.net/minerals/silver.htm

6. The Discovery of Metals. (2012, June 21). In AZO Materials. Retrieved from https://www.azom.com/article.aspx?ArticleID=6101

7. Michaud, D. (2016, September 26). Silver Rocks and Minerals. Retrieved from https://www.911metallurgist.com/blog/silver-rocks-minerals

8. Pappas, S. (2014, December 11). Facts About Silver. In Live Science. Retrieved from https://www.livescience.com/37040-silver.html

9. STATUTE-79. (1965, July 23). Retrieved from https://www.govinfo.gov/content/pkg/STATUTE-79/pdf/STATUTE-79-Pg254.pdf

10. Mining (2019 Encyclopedia Britannica, Inc. ://www.britannica.com/technology/silver-processing

10. Skinner, B. J. (2015, August 13). Mineral deposit. In Encyclopaedia Britannica. Retrieved May 3, 2019, from https://www.britannica.com/science/mineral-deposit/Hydrothermal-solution

11. Hackly (2019). In Minerals.net. Retrieved from https://www.minerals.net/mineral_glossary/hackly.aspx

12. Isometric (2019). In Minerals.net. Retrieved from https://www.minerals.net/mineral_glossary/isometric.aspx

13. Native Elements (2019). In Minerals.net. Retrieved from https://www.minerals.net/mineral_glossary/native_elements.aspx