If you are in the world of precious stones, gems and mineral collection, you will have come across the terms agate, chalcedony and jasper. These minerals cause confusion because visually they are very similar, however, they have slight differences that we will learn in this article, so that you can correctly define these stones.
Summary table: differences between agate and jasper
Let’s remember that both agate and jasper are a variety of chalcedony and microcrystalline quartz, which are differentiated by the following:
| Characteristics | Jasper | Agate |
| Diaphaneity | Opaque | Translucent, semi-transparent |
| Impurities | Mayor | Minor |
| Bands | It has not | It has |
| % chalcedony | Minor | Mayor |
What is chalcedony?
First of all, you should know that the term chalcedony stone is given to mineral materials that are composed of microcrystalline quartz, and all varieties of agate and varieties of jasper are made up of microcrystalline quartz and are therefore a variety of chalcedony.
Chalcedony characteristics
The chalcedony Being made up of silica, it is a very hard and quite durable material, for this reason, it was used to make cutting tools and weapons, a great example of this is flint stone.
Chalcedony can occur in a wide range of colors, for example, gray, white, red, orange, yellow, brown, and black. It can also occur with bands, dendritic sections, speckled and mossy structures inside.
Chalcedony always fractures in a conchoidal fashion and therefore its faces always have smooth and curved surfaces and thanks to this it is that its luster is dull to waxy, unlike a crystalline quartz which has a vitreous and brilliant luster.
What is microcrystalline quartz?
To understand what chalcedony means, one must first understand what microcrystalline quartz is. It is worth mentioning that quartz is a mineral composed of silica (SiO2)
Microcrystalline quartz is a variety that occurs in very small sizes and can only be visualized with the help of a petrographic microscope. It can be said that they measure even less than 0.5 millimeters.
What is agate?
Now we know that the agate stone is a variety of chalcedony that is characterized by being translucent to semi-transparent. You must bear in mind that the agates are presented with microcrystalline quartz material distributed in bands.
Therefore, a chalcedony that has bands is an agate. Many times, these bands are not very visible, but seeing the difference in colors between bands with a geologist’s magnifying glass, this mineral can be distinguished.
To differentiate the agate from the jasper, transparency must be taken into account, the agate is translucent to semi-transparent. This means that if you look through the gem you will see distorted or blurred images since the light does not pass 100%.
How is agate formed?
The on all fours They are formed related to volcanic activity where aqueous hydrothermal fluids rich in dissolved silica precipitate microcrystalline quartz in cavities in any type of rock.
Microcrystalline quartz precipitates concentrically from the rock walls. The bands appear with different tonalities due to the impurities of other minerals and also due to the variation in the size of the quartz crystals.
What is jasper?
The jasper stone is also a variety of chalcedony, however, unlike agate, jasper is characterized by being opaque, meaning that light does not pass through the mineral.
Naturally microcrystalline quartz is semi-transparent, however, when small impurities of foreign mineral materials adhere, then microcrystalline quartz changes its ability to transmit light and it decreases considerably.
In this case, jasper usually has many types of impurities in its composition that make it naturally opaque.
How is jasper formed?
Jasper is generally formed by cementing very fine materials of sedimentary and volcanic origin with silica. In this case, the silica suspended between those particles precipitates and unites them in an opaque mass called jasper.
Flint is the best known jasper material and it forms as extensive layered deposits, which were used to create tools.
The cementation process is sometimes so aggressive that sediment, ash, or volcanic particles dissolve or recrystallize into microcrystalline quartz.