The advice following may help, especially the words I have underlined, but this was written over seventy years ago.
'Consist of' = 'is made of; 'consist in' = 'is'. 'The trifle consists of fruit, cream and jelly'; 'Goodness consists in being honest, true and kind'.
It follows that (i) consist 'of' is always followed by the name of a stuff or material, and (ii) the substitution of 'is' or 'is made of' is an effective test. Thus in the first sentence 'is' would makes sense, but is not idiomatic; in the second, 'is made of' would scarcely make sense.
In the following sentence [...] the 'is made of' test reveals the error: 'The most exceptional feature of Dr. Ward's books undoubtedly consists of the reproduction of photographs.'
Treble, H A and Vallins, G H (1936) An ABC of English Usage, Oxford:OUP