Rainbow obsidian (galtovka 26 - 34 mm), Hidalgo state, Mexico

The cost for the smallest sample.
26mm-length
34- 9,11 grams - galtovin weight
The cost with a choice from 27 rubles to 230 rubles.

Any stone can be "dressed" in a special spring for the stone - (holder), so you get a ready-made pendant.
Links to springs here:

www.livemaster.ru/item/32005533-materialy-dlya-tvorchestva-pruzhinki-dlya-kamnya-krupnye-pod-serebristye.
www.livemaster.ru/item/32008713-materialy-dlya-tvorchestva-pruzhinki-dlya-kamnya-krupnye-pod-zolotistye..

An excellent galtovka of rainbow obsidian (rarely found) is presented with iridescence in green, blue, purple and reddish tones, sometimes alternately iridescent combined in one stone.
In the photo, galtovka "poses" from the best angle of the irrigation.

Being a mixture of different minerals, this rock, consisting of volcanic glass, is chemically and morphologically extremely variable. This is an igneous, effusive (poured out) material, the location of the stripes on the stone indicates the direction of the lava flow.
The most characteristic and amazing properties of volcanic glasses are the ability to swell, bubble when heated (burn in fire), as well as the ability to split into narrow fragments with sharp cutting or piercing edges.

Obsidian with iridescent (iridescent), silky, silver-mother-of-pearl or golden tint is especially appreciated, due to the presence of the smallest gas or crystal inclusions.