volcanic sand

I was told this is good for insulation, is this true? do you know how it compares to perlite, is there a simple way to test this?
Also did anyone make cob from this ?, i tried but find it difficult to mix as it is very light and the mix remains porous.

Volcanic sand is also known as black sand, not particulary light or insulating. The stuff you show is white or greyish and very light, even when mixed with clay it remains light and porous. This does look a lot like perlite to me, ideal for high temperature insulating purposes.

They called it sand ,but it is volcanic ash , not sure the different types there are, but this fell from high altitude last year from the chilean volcano eruption , that is where it comes from.

I wonder how it compares to perlite, is there an easy way to test?

Also, i tried to make mortar with it, looks good to me, do you think it can be used to bond the firebricks?or regular sand is better?

Ah... Volcanic ash is a good insulator, ideal for insulating a rocket stove. Even wood ash will insulate in a reasonable way but it will compact over time. This volcanic stuff can be mixed with clay slip to avoid compacting, I guess. It's possible this ash is alright for mortar as well, I am just not sure about that.