FMF - Friends of Minerals Forum, discussion and message board

[preciousgem]

Is it possible to determine by visual examination aided by magnifying glass if a gem stone carving in shape of an art object is made of jadeite or quartzite, especially if color enhanced, or it needs gemological lab identification?
I read that quartzite gem stones have a composition of different minerals, chemical components and would like to know how the lab ID might be influenced by the multitude of components and how the lab will identify each component separately, or determination is based on the mineral or chemical component that represents the majority percentage in quartzite.
Thank you in advance,
Michael

[keldjarn]

I think it may be difficult to determine for sure just by a visual examination if a carving is made of jadeite or quartzite, but jadeite has a hardness of 6 and Quartz 7. Thus with a small quartz crystal it should me possible to scratch jadeite - but it would be more difficult with quartzite ( still being a rock rather than a pure mineral, quartzite may contain small flakes of mica etc which can give the impression of a reduced hardness. )

[John S. White]

I agree that it can be quite difficult to make an absolute determination using simple tests. If the object is dyed quartzite then you might try to dissolve some of the dye using various relatively common solvents. Apply the solvent to a small area, let it sit for a few minutes, then dab it up with a paper towel to see if any color comes off. Of course your object could be dyed jadeite in which case this test doesn't really help in identifying what it is, just that it has or has not been dyed.

[lluis]

Good afternoon

Talking from what I remember of when I was working by a gem dealer (when young,; say, when still tyhe dinosaurs were in earth...), jadeite is very difficult to polish completely homogeneously. It usually have at least tiny spots of greasy aspect among the shiny mass.
Quartzite polish evenly.

So, in principle, if any greasy spot, it is jadeite. If not, could be both still.... (but more probably quatrzite)

With best wishes

Lluís