Does Volcanic Sand alter PH?

[The Masked Shadow]

Does volcanic sand alter PH? I’ve read that it does.

 

[FJB]

If it is basaltic (true black volcanic sand), it should not. Other volcanic sands (andesitic or granitic) should not either.
Mixtures including carbonates will affect your pH (raise it).

 

[duanes]

Although I know its not sand, I have used lava rock as biomedia for over 30 years and never found it to alter my tanks pH..