Question regarding slurry stone ...
With eschers, is it a problem if you use a slurry stone that is a different color than the hone? e.g., using a dark grey slurry stone on a yellow-green hone? Or are the grits so similar that there is not problem mixing?
Also, while Tim initiated this thread in early 2009 suggesting a study to determine different honing qualities of the various colors, it doesn't seem that any results were ever posted to the thread.
I have seen several suggest that the differences are "subtle" ... meaning what? Darker is more abrasive/faster, or yellow/green is smoother, etc.?
Any help would be appreciated as I am looking at a purchase.
THANKS !!!
Correlation of color to chemistry and value of Garnets
Hi guys,
I am in no way an Escher connoisseur nor know anything about it, but I spent an hour or so with Richard this weekend (thank you kindly Richard) who kindly provided me with some history behind some of what he knows about Eschers.
Anyways, being as it may and given the indisputable fact that color is a direct reflection of the physical and chemical properties of "materials" (in this case garnets), the topic got me curious to point that I started to do some "quick & dirty" research about the properties of garnets.
Here's the scoop:
Garnets are found in many colors including red, orange, yellow, green, blue, purple, brown, black, pink and colorless...now, we do see these color combinations within the Echers, don't we ;)??
Caveat in describing color: When we discuss color, we have to be careful about defining what kind of light the observations are made. It changes color from blue-green in the daylight to purple in incadescent light, as a result of the relatively high amounts of vanadium (~1 wt.% V2O3). Other varieties of color-changing garnets also exist...e.g., in daylight, their color ranges from shades of green, beige, brown, gray, and blue, but in incandescent light, they appear a reddish or purplish/pink color.
Getting back to the garnet story:
Chemical structure and color chart:
Garnets are nesosilicates having the general formula X3Y2(SiO4)3. The X site is usually occupied by divalent cations (Ca2+, Mg2+, Fe2+) and the Y site by trivalent cations (Al3+, Fe3+, Cr3+) in an octahedral/tetrahedral framework with [SiO4]4− occupying the tetrahedra. As I understand it, there are several types of garnets with different color properties (below):
- Almandine: Fe3Al2(SiO4)3 - Red color
- Pyrope: Mg3Al2(SiO4)3- deep red to almost black
- Spessartine: Mn3Al2(SiO4)3 - orange/yellow
- Andradite: Ca3Fe2(SiO4)3- red, yellow, brown, green or black
- Grossular: Ca3Al2(SiO4)3 - green, cinnamon brown, red, and yellow
- Uvarovite: Ca3Cr2(SiO4)3- bright green
Just a tidbit...This may explain the rich source of different garnets (and their color variation) in the hot Eschers everyone is so hot to talk about. So, if you have a Y/G, you may have a stone with any combination of Ca3Fe2(SiO4)3 , Mn3Al2(SiO4)3 , Ca3Al2(SiO4)3 , or Ca3Cr2(SiO4)3.
Anyone up for analyzing the mineral contents on these stones? better yet, does anyone want to chip off some part of their $$ stones and donate them for such an analysis :rofl2::rofl2:?
Questions I have are:
1. Do any form of garnet have a temporal (age) component to them? i.e., is any one older/younger (in millions of years) to another
2. Does this temporal component (if valid), be more valuable compared to another?
Mind you, this is not coming from an expert in stones or an inorganic chemist.