Please would you explain what you mean by 'lava glass'? http://www.lavaglass.co.nz/
Also when and where did your father aquire this glass?
It reminds me of glass which is made in America but externally decorated by painting but the colours on yours seem integral.
Also there is some glass made which incorporates ash from volcanos.
So you see that the more you can tell, the better!!!
There are some very expert people contributing to this board so
good luck, Ruth