Featured Black and White Onyx? Necklace

It is clear to me that the clasp means that this 32-inch necklace of alternating black and white stones is not a commercial product. Probably made by an artist or hobbyist or from a country that makes simple jewelry. What interests me are the stones - they are 1/2 inch long and well polished. The white ones are almost translucent, and some have tiny black dots. Are these agate or onyx or is there no way to tell? If you have a chance to glance at this post and respond I would appreciate it.

 

White quartz and?????

 

You got me

 

Me too.

 

My guess would be white quartz. So much white quartz is dyed that we rarely see the natural form (or perhaps that is bleached?). No expert, but that's my 2 cents!