Reference:

ABOUT OPALS

 

What is a Matrix Opal ?

 

 

The correct definition is Natural Opal Type 3

Natural Opal Type 3 – is opal presented in one piece where the opal is intimately diffused as infillings of pores or holes or between grains of the host rock in which it was formed. This opal is commonly known as matrix opal. (See figure 3C).

Boulder matrix opal is found in Queensland and can be distinguished by the ironstone host rock.

	Fig. 3. Types of natural opal. C. Natural opal type 3 (Matrix opal) (Photographs, R. Weber).

 

Find more information at the OPAL Association's Opal Nomenclature Section of their Website:

http://www.opal.asn.au/information_nom