This is a question I get asked a lot. It took me a long time to learn the difference between jasper and agate. There are still some times when I get confused, but it seems that geologists can also get confused between these two classifications of stone.
Basically they are both made up of microcrystalline quartz. According to Hobart King, geologist at RockTumbler.com, “the word microcrystalline means that the quartz is in the form of crystals that are so small that a microscope must be used to visualize them individually.”
I have linked the article above because it is a very clear and concise explanation of jasper and agate. (He throws in chalcedony as well but I’m keeping it simple here.)
Both jasper and agate are forms of chalcedony, as well as being classified as quartz (SIO2.
Agates are translucent to semitransparent and jaspers are opaque.
Agates, according to Mr. King, “form in areas of volcanic activity where waters, rich in dissolved silica (quartz) flow through fractures and cavities in igneous rock. When the solution is highly concentrated with dissolved silica, a silica gel can form on the walls of these cavities. That gel will slowly crystallize to form microcrystalline quartz.”
Impurities within the silica create the colorful bands in agate over time.
Jasper is formed when there are enough impurities or foreign matter to make the rock opaque.
Again, Mr. King writes, “jasper often forms when fine particulate minerals are cemented together by the silica gel.”
I would encourage you to go to the article and read the entire thing for more interesting information.
Some Notes on Healing Uses
While my interests in rocks and crystals came from a purely metaphysical space, I find the geology fascinating as well.
In reading the article mentioned here, I had a few insights on how I might use some of these stones going forward. (Or why I use them in the way I do.)
Jasper has always seemed to work exceptionally well on the denser physical level of the body. It penetrates that denseness and gets to the heart of what has manifested as a physical problem or symptom.
Agate, on the other hand, often works with the more fluid nature of the emotions.
Together I feel they make a healing matrix that can be used to get to the heart of a physical problem, and to work with both the symptoms and the root cause.
In both cases, if you are a collector focused on the beauty of Mother Earth, you can’t do better than to have these beautiful specimens in your collection.