What Is That Gem or Jewel?

The 1st Edition of AD&D Dungeon Master's Guide is a wonderful resource for any referee to possess. In the section "Money (Gems & Jewelry)" there are roll tables  for determining the precise values and types of gems and treasures rolled.

These sadly don't exist for my preferred edition: B/X. Specifically, OSE has this to say on Gems and Jewellery.


The value of each gem in a treasure hoard is determined by the following table:

d20Gem Value


Each piece of jewellery indicated by a treasure type is worth 3d6 × 100gp (or more, if the referee wishes, for characters above 3rd level).

Damaged Jewellery

Rough treatment of jewellery (e.g. crush-ing, intense heat or fire, lightning) can damage it, reducing its value by 50%.

— Old-School Essentials Core Rules under Gems and Jewellery

We're going to have a much easier time lining up the rules for gems than the rules for jewellery. Gems in the DMG are listed in the categories:

Jewellery is resolved very differently however. It is given a d10 value ranging from 100gp to 12,000gp (it's actually a d100 table, but each result is an even multiple of a 10% chance).

This might be the 'or more, if the referee wishes, for characters above 3rd level' that the book talks about. As Jewellery in Basic edition ranges from 300gp to 1,800gp in value, significantly less than the range of AD&D1e.

Interestingly, this lines up with the definition given in AD&D1e for the value of Wrought Gold jewellery, which is found on a roll of a 3 or 4. It might simply be that all jewellery in Basic edition is expected to simply be shaped gold.

This is an elegant solution, and works nicely with the silver-standard revised system I use, where I can simply say that 'jewellery is made of silver'. Though I do like the posibility for lower and higher grade of treausre to exist, and to account for the expert-edition level ranges and their never stated expectation for more valuable jewellery.

So, for gems, simply consult Page 26 of the AD&D1e DMG for treasure the values and descriptions of different gems. I'm not going to reproduce it in full here as you can go out and buy the book if you want this content and I don't want to get into an IP trouble. But here is a list of gems for each category:

It also has some gems valued at 5000gp, which can't occur on the OSE gems table. Perhaps I'd have one of these show up if after rolling a natural 20 for the most expensive gems, I rolled again and got another natural 20 (1-in-400 chance).

Now for Jewellery, falling between 300 and 1800 does give us the nice catch all of "it's all just gold" (or silver, in my case). But I'd like to see some variety given the boundaries of the table are quite wide.

If we look at the original table, 50% of jewellery types that do not exceed 1800gp are gold. Let's keep this number, and divide evenly by the other two, giving us a quite nice table to start with, ivory or silver on a 1, electrum on a 2, and gold on a 3 or 4. However, we want there to be the possibility to get higher grade metals. Jade, coral, platinum, and gemmed silver are all able to be worth 1800 or under (gemmed gold, and gemmed platinum exceed the 1800 minimum). Of these, jade, coral, and platinum are 5d6×1005\text{d}6\times{}100 gp in value, that will yield something beneath 1800 pretty much exactly 60% of the time, so ets give that a weights of 35\frac{3}{5} (compared to the 1 and 2 weights we've given everything else). Gemmed silver is the only other result to consider, which is 1d6×10001\text{d}6\times{}1000 gp, we could naievely give this a value of 16\frac{1}{6}, but 1800 is almost 2000, so we should probably consider how much of the graph is really likely to be under 1800 if all values could generate on the curve (instead of just 6 discrete points). Fortunately those upper bounds are an easy to calculate straight line, so we know that 1800 should be around 310\frac{3}{10}.

For the same reason we exclude our high end somewhat, we must exclude our low end somwhat also. We will not generate gems with a value of less than 300, and so electrum, silver, and ivory are all slightly less likely. There's an 80% chance that 1d10×1001\text{d}10\times{}100 is equal to or larger than 300 for ivory and silver. There's a 3536\frac{35}{36} chance that 2d6×1002\text{d}6\times{}100 is equal to or larger than 300 for electrum.

All of this together, gives us the following table, with conditions for a reroll

01-09Ivoryless than 1000gp value
10-18Silverless than 1000gp value
19-39Electrumless than 1200gp value
83-86Jademore than 500gp value
87-90Coralmore than 500gp value
91-94Platinummore than 500gp value
95-00Gemmed Silvermore than 1000gp value

Then, as for which type of jewellery it is, we'll just randomly select from the examples given in the 1eDMG.


And as a bonus to myself, here's one more reasonable for my adjusted metal values where silver is significantly more more valuable and gold even more so (100:100:100 instead of 10:10:10).

01-09Ivoryless than 1000gp value
82-87Jademore than 500gp value
87-93Coralmore than 500gp value
94-100Goldmore than 1000gp value

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