Chalcedony Species Part 3 - Dendritic Agate & Moss Agate

Hi everyone,

Welcome back to the next in our series of Chalcedony.  Today I would like to discuss dendritic agate and moss agate.  These stones I find very interesting in their colour and the way one can use these stones to create very interesting works of art.  The way that these stones are cut and polished makes them look like ferns or landscapes.  The colour are rich and intense.  I think that these stones are very unusual and unique.  I hope you enjoy learning about these stones and that you have fun as well.  As before all the information being used in this blog is from the book Gemstones of the World by Walter Schumann.

Dendritic Agate

Dendritic agate is usually colourless or a whitish-grey colour.  The chalcedony is translucent usually with tree or fern-like markings.  The name is derived from the Greek dendrites meaning tree-like.  There are some people who feel the term agate is not correct as this stone has no bandings, however must people do not consider the term to be misleading.  The dendrites are iron or manganese inclusions and are usually brown or black in colour.  This look is formed in very fine fracture surfaces through the crystallization of weathered solutions in the neighbouring rock.  The dendritic chalcedony are found with other chalcedonies.  The deposits are normally found in Brazil, India, and the United States.  There are scenic agate which is a dendritic agate in which the dendrites resembles landscape-like images in brown or reddish colour tones.  Then there is the mosquito stone.  This is where the dendritic agate has ball-like growths which is reminiscent of swarms of mosquitoes.  These types of stones are used for rings, brooches, and pendants.

Scenic Agate

Mosquito Agate



Moss Agate



Moss agate is a colourless chalcedony with green, brown or red inclusions.  The colour streak is white and the Mohs hardness is 6.5-7.  The density is 2.58-2.64 and there is no cleavage.  The crystal system is trigonal microcrystalline and the chemical composition is silicone dioxide.  Moss agate is translucent and has inclusions of green hornblende or chlorite in a moss-like pattern, hence the name.  The moss agate that has the red and brown colours are from the oxidation of iron hornblende.  As above the name agate is generally accepted even though there is no banding.  The appearance of the stone occurs through filler in fissures or as pebbles.  These rare gems are found in India, China, Russia and Colorado.  Most often used as plates, cabochons for rings, brooches, and pendants.



Moss Agate Rough



I hope everyone enjoyed this journey of discovery into the world of dendritic agate and moss agate.  I had fun learning about the new information discovered.  I would like to hear from you.  Please let me know what you think about this post or any others that I have done.  Until next time.

The rare gem lady