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Obsidian dispersion


#1

I can’t find the dispersion of obsidian , in the gem list can any one tell me what it is please ?


#2

Walter Schumann in his Gemstones of the World lists the dispersion of obsidian as 0.010.


#3

Thank you soooooo much :slight_smile:


#4

Dispersion is at its simplest the difference in the Refractive Index between red and ultraviolet light. Measuring this characteristic required homogeneity of the crystalized, transparent material. Witness the difference between cheap glassware and lead-glass crystal. The former demonstrates little dispersion while the later is stunningly dispersive. Having said that, the reference to obsidian, i.e., volcanic glass, a material of no set composition or clarity. The lack of a figure representing obsidian’s dispersion reflects the fact the there is not set composition for obsidian. Hence no mention of the dispersion <obsidian, type xx>.

Ref. < Hodgkinson, Alan. The Journal of Gemology; London Vol. 34, Iss. 4, (2014): 281-283.

Bob Ritchie


#5

Thank you Bob , i appreciate your input:)