Hi there Yisheng,
A simple short question, with a long complicated answer!
I found your question very interesting from a "psycho-linguistic" point of view.

As you all know, I'm not literate in Chinese the way most of the readers here are. I had one hour a week of Mandarin tuition in the evening, with a home tutor arranged by my parents. I found it extremely annoying to have to do (as a kid of 10-12), and never put much effort into it. [ Of course I regret that now, and will be starting to do a Mandarin course this September. ] So I just never got beyond: "This is my elder brother", "Please come in" etc... (plus learning the characters, but no pinyin, because I don't think anybody did pinyin in Malaysia in the 1970's).
What I found interesting was the way you phrased your question, and the way I would "re-interprete" it.
You think: "How would <X> pronounce the _character_ for jade". In contrast, I think: "The way to write the Hokkien _word_ for jade - "gek8" - is three strokes across, one down (=king) then a dot at the right bottom", and I think: "Oh, and by the way, the 'word' "giok8", which I only ever see in personal names, happens to be the literary pronunciation of "gek8", because Hokkien has this fascinating phenomenon of colloquial vs. literary pronunciations".
For me (being non-literate), the spoken form is the primary thing. There are two words which REALLY ARE "gek" and "giok", and the king with a dot is the way of writing them in characters, whereas for you, it is sort of the other way around - the king with a dot can be pronounced "gek" or "giok", depending on context.
In fact of course, one might say that yours is the "more correct" way of viewing the situation, but both views are not really that different from one another - just a difference in emphasis. Still, I found it interesting enough to devote some words to it.
To answer your question explicitly though, for me, the word for the stone / substance is only ever "gek", which I would use in the context of a ring, bracelet, pendent, earrrings, or for a jeweller dealing in jade, or for an art object carved from it. As I more or less said above, I'm only familiar with "giok" in personal names, and it was much later (say when I was in my early 20's) that I started to realise that they were related in any way. This came at about the same time as the realisation about "gueh8" vs. "guat8" for "moon" (and perhaps a few other personal names which I can't think of at the moment).
Even then, from my 20's to my early 40's, I thought that literary pronunciations were only used in personal names. My *final* realisation of the extensive use of literary pronunciations in the "normal" language only came when I started reading linguistics texts on Minnan, and all the wonderful *details* I've managed to get here on this forum on this subject. [ The linguistics texts I have read tend to only mention the subject of colloquial vs. literary pronunciation, and give a few examples. On this forum I get even more specific details, relating to words in know _in real life_. ]
For example, I had known the phrase "put8-hau3" (lacking in filial piety) since my childhood, but it was only on Minnan-related internet pages and here that I found out that "put" was the literary pronunciation of "m".
>> I never knew about three of the common ones (不 (m and put),
>> 人 (lang and jin), 有 (u and iu)) before reading Hong's link, so that was
>> great. From my childhood I (sometimes!) heard a phrase "put1 hau3"
>> (="lacking in filial piety"), where I knew that "hau3" means "filial piety".
>> Would I be right in guessing that this "put" is 不 ?
The above extract is from a posting to this forum on 21 November 2003. [ As you can see, I hadn't even mastered Hokkien tone numbers properly at that stage, and wrote "put1"! ]
Once again, I'm *so* grateful for this forum, and for all the things I can learn from you people. [ PLEASE correct my tone numbers when I write them incorrectly! ].
Cheers,
-Sim.
[%sig%]