Instance-Type Relation In Nominal Group Realising Value

Basalt	is	an example of a volcanic rock
Token	Process: identifying	Value

Note that this is an identifying clause realising the identity of an example

— the identity relation in the clause obtains between basalt and an example […] —

not an attributive clause realising the relation between an example and a type.

The relation between example and type is realised in the nominal group realising the Value:

an	example	of	a	volcanic	rock
Variety			Deictic	Classifier	Thing
Premodifier	Head	Postmodifier

That this is indeed the case is demonstrated by the fact that the removal of the meaning of an example of yields an attributive clause:

Basalt	is	a volcanic rock
Carrier	Process: attributive	Attribute

Cf

This sample	is	a volcanic rock
Carrier	Process: attributive	Attribute

The above demonstrates the difference between an identifying clause with an example of and an attributive clause.