Are these three questions on gemstone size and value duplicates?

Question

How big is a 5,000gp diamond?

and

How big is a gemstone in the dmg gemstone table?

and

How big is a 50 gp diamond?

These three very related questions are potentially a triplet of duplicates. Rather than an open-close cycle, it seems a good idea to discuss here.

Answer 1

The questions about the (value) gp diamonds are duplicates of the more general question about gemstones.

First, let us examine the question, How big is a gemstone in the dmg gemstone table?

The question is given:

Is there indeed a standard gemstone size in the DMG's treasure tables, and if yes, what is it?

In the most literal sense, this is just asking if the tables say anything about sizes, which they do not. But this question is given with significant context, including the conclusion that no, the tables do not include size. The querent goes into more detail:

I do not require a strictly RAW answer to this question. There does not seem to be guidance on this issue within the official rules, but I can think of three possible ways of answering this question, in order of authority:

1. Inference from official adventure modules that contain a description of a gemstone’s size and value. To get at the pure value of the gemstone as a material, such a reference should not be to gemstones that are part of an art object
2. Inference from real world gemstone value, applied to the RAW. This SE answer to a similar question has some helpful guidance.
3. If nothing else, a secondary source with more usable gemstone tables would be helpful. This includes previous editions, thoughtfully written homebrews, and third party publications.

All I want is a number that is plausible, based on either real life or existing D&D materials.

It is quite clear from this that the question being asked is decisively not "do the gemstone tables give sizes?". Rather, it seems quite clear that the question being asked is something like: "What is a reasonable estimate for the size of the gemstones given at each price point in the DMG?"

Next, we will examine the questions How big is a 5000 gp diamond? and How big is a 50 gp diamond?, and see if they are actually asking the bolded question above.

Each question includes some context about spell components, and then asks nearly identical questions:

How big would a diamond worth 5000 gp be?

and,

How small would a diamond be that is only worth 50 gp?

Both of these questions are substantively identical to the question "What is the size of a (value) gp diamond?" And since nobody is asking for unreasonable answers, I claim that this is substantively identical to the question, What is a reasonable estimate for the size of a (value) gp diamond?

Finally, to tie it all together, we observe that 50 gp and 5000 gp diamonds appear in the gemstone tables in the Dungeon Master's Guide, so they are each answered completely by the question, How big is a gemstone in the dmg gemstone table?

The Duplicate Criteria

This faq question details how we should close questions as duplicates. There are three criteria, which we will examine in turn.

First criterion:

It's the same question, or Question A is already covered obviously as a subset of Question B. Obvious here means I can tell at a glance it's there.

This one seems to be satisfied, as I have demonstrated that the (value) gp questions are very obviously subsets of the general question.

Second criterion:

Question B has an obvious answer to Question A. Obvious here means I get a straightforward answer without hard searching — a couple of sentences buried in the middle of a post, or an answer which only sort of implies an answer to Question A, doesn't count as obvious.

The answers to the general question make exactly the same arguments as the value specific questions - all three questions have essentially the same answers given.

Third criterion:

There is not some strong compelling reason to covering Question A alone, separately from Question B. (If the above bullet points are met this rarely happens.)

I assert that there is no strong compelling reason, especially given that the first two criteria are met. A dissenting answer must give this reason, and it must be particularly compelling.

On timing and canonical quality.

The meta guidelines for duplicates also has a statement about timing and which question to leave open:

We prefer closing newer questions a dupe of older unless there's a major quality benefit the other way around. Some examples of when there's such a quality benefit:

• The older one isn't answered (or has bad answers), and the new one has good answers.
• The newer question is flat-out better written, easier to follow, and generally more useful for anyone interested in that line of inquiry. Answers to it are equal or better ("both have no answers" is equal).
• This typically occurs when we establish a high-quality canonical question to handle a subject straightforwardly that's previously been handled messily in various earlier questions.

The question about the 50 gp diamond is the oldest of the lot, but the general question about gemstone values in the DMG is head-and-shoulders above the others in terms of quality. It gives detailed commentary on the querent's own investigation into the problem and outlines for us what makes a good answer to the question. Further, it is more general and has the potential to cover a wider range of future duplicates than the other questions. I will have an easier time convincing you that a question about 500 gp rubies is a duplicate of this general question about gemstones than I will to convince you that a question about 500 gp rubies is a duplicate of a question about 50 gp diamonds.

I propose we close the two questions about diamonds as dupes of the question about gems found in the DMG.

Answer 2

These are not duplicate questions.

How big is a gemstone in the DMG gemstone table?

Is asking for guidance in wide array of potential options, some of which have 5e answers and some do not. The accepted answer uses a table from ADnD 1e. While that is understandable because of the breadth of the question doesn't offer a precise answer in the current edition.

How big is a 5000 gp diamond?

However asks for 1 specific diamond value. Importantly a diamond used in a spell so that it could be important for a spellcaster to know the specifics of how easy it is to store or handle. Also importantly, there are at least two examples of it being described in DnD 5e in official sources. Meaning this question can be answered much more accurately than the previous one.

The comparison would be if someone asked "How big are cities in the Forgotten Realms?" vs "How big is Waterdeep in the Forgotten Realms?". The answer to the first is almost certainly going to be generalized to a point where it is unlikely to include an answer to the second, even though the second can be answered much more accurately (and could be much more important to have an exact description for a given campaign).