Descriptive adjectives before or after the noun
I know that generally, descriptive adjectives come after the noun, while adjectives of quantity come before the noun.
Tengo un libro viejo. (viejo describes a quality of un libro and thus comes after the noun)
Muy pocas personas hacen eso. (pocas defines the quantity of personas and thus comes before the noun.
However, I read on studyspanish.com that if a descriptive adjective "speaks of a quality that is inherent and usually taken for granted", it does not go after the noun, but before.
Here is my question: Does the above mean that you would say "un gran elefante", but "un elefante pequeño"? My logic is that an elephant being big is usually taken for granted, while an elephant being small is not.
How about "un pequeño ratón" and "un ratón grande"? Or "una joven niña" and "una niña vieja"?
"un gran elefante" means "a great elephant", not "a big elephant". There are a handful of adjectives that change meaning depending on if they come before or after the noun, and "grande" is one of those.
As for the "inherent quality" issue, one example would be that Snow White in Spanish is Blancanieves - literally "white snows", not "snow white". Snow is inherently white.
My unscientific polling of Google Mexico found about ~90,000 results for both the phrase "niña joven" and "joven niña", with the latter being somewhat more common. An example there would be Anne Frank: Diary of a Young Girl is translated as "El diario de una joven niña".
But it doesn't seem to be a requirement, as "niña joven" is also used.
Thank you. Does this mean you're free to decide for yourself, depending on whether you yourself find the quality inherent to the object or not?
Native speaker here. There are (as ceaer said) some cases in which the meaning changes (sometimes it is a minor change), despite being a native speaker I could not make a list of them but I'm sure that you can easily find info about this exceptions. About deciding if the quality is inherent or not it depends on the context, most of the time placing the adjectives before the noun sounds more poetic and is most commonly used in literature as a writing technique (it would be strange to hear someone talking like this) but it does not change that both are correct.
When we (native Spanish speakers) learn English, they tell us that adjectives come before the noun as opposite to Spanish, I guess this could be also taken in account the other way around but not forgetting about those exceptions.