Your Questions About Agates

admin answers:

Http://www.agatelady.com/agate-basics.html

admin answers:

That is a large range.

Raw agates, and sometimes even cut/polished ones, can sell for anywhere from fifty cents (american) to several hundred dollars.

It depends on the quality of the agate, the type of agate, the clarity / color / flawlessness of the patterns, and of course how much artistic work has gone into its final production.

Large and dramatically patterned / colored agates are worth the most.

admin answers:

A rock and mineral shop.
Maybe a university (doubtful though).
EBay.

admin answers:

Most agates occur as nodules in volcanic rocks or ancient lavas where they represent cavities originally produced by the disengagement of volatiles in the molten mass which were then filled, wholly or partially, by siliceous matter deposited in regular layers upon the walls. Such agates, when cut transversely, exhibit a succession of parallel lines, often of extreme tenuity, giving a banded appearance to the section. Such stones are known as banded agate, riband agate and striped agate.

The first deposit on the wall of a cavity, forming the "skin" of the agate, is generally a dark greenish mineral substance, like celadonite, delessite or "green earth", which are rich in iron probably derived from the decomposition of the augite in the enclosing volcanic rock. This green silicate may give rise by alteration to a brown iron oxide (limonite), producing a rusty appearance on the outside of the agate-nodule. The outer surface of an agate, freed from its matrix, is often pitted and rough, apparently in consequence of the removal of the original coating. The first layer spread over the wall of the cavity has been called the "priming", and upon this base zeolitic minerals may be deposited.

Many agates are hollow, since deposition has not proceeded far enough to fill the cavity, and in such cases the last deposit commonly consists of quartz, often amethyst, having the apices of the crystals directed towards the free space so as to form a crystal-lined cavity, or geode.

On the disintegration of the matrix in which the agates are embedded, they are set free. The agates are extremely resistant to weathering and remain as nodules in the soil or are deposited as gravel in streams and shorelines.

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Hope that helps a bit, Goodluck
DT

admin answers:

Agate & Quartz are both composed of SiO2 or silicon dioxide.

Agate is a cryptocrystalline version of quartz.(very small, as not to be seen with the naked eye, crystals)

Agate is formed in sedimentary deposits from dissolved quartz that is redeposited. This is usually near the surface where there is lower pressure & temperatures.

Many times agate is found as geodes. These are really cool. Sometimes they fill in completely w/ layers of silica. Other minerals may be present as to make color bands. Other times the geode will not fill completely in before crystals start forming. WOW! Love these!

Sometimes from the process mentioned above, cryptocrystalline silica will seep into bones & remnants of tree trunks. Ever seen petrified wood? OF course this is not the only mineral that will do this in wood & bones.

Opals are also a variety of quartz. It contains minute amounts of water in its structure. The only difference here is that opals are amorphous meaning that there are no crystals.

Silicon Dioxide is the most abundant mineral in the earth's crust. It is found everywhere and in all kinds of forms.

🙂