Ornamentation: Polishing Gems

Hope Diamond, By David Bjorgen

Hope Diamond, By David Bjorgen (Own work) [GFDL, CC-BY-SA-3.0 or CC BY-SA 2.5-2.0-1.0], via Wikimedia Commons

Creighton Broadhurst of Raging Swan Press (I like Raging Swan products) wrote a post last week about Gygax On… Treasure, speaking mostly of how most treasures are likely to consist of a collection of varied but valuable items, rather than a simple chest full of coin or pouch of gems. Coins and gems will probably be involved, as might jewelry and objets d’art, but there might be trade goods (barrels of wine, furs) or luxury items (such as spices).

One of the items listed was “a two-handed sword (with silver wire wrapped about its hilt and lapis lazuli pommel to make it worth three times its normal value)“, and it occurred to me that I haven’t seen guidelines to help make items like this. I’ve seen guidelines for randomly generating weapons (possibly masterwork), and for jewelry (though often that just identifies the gold piece value range and suggests items that might be worth that value), but never really any tables for generating ‘decorated items’.

I started to write a post about this, then realized it’s likely to run pretty long. Thankfully the topic almost naturally splits itself up, at each stage I can add another piece. In good programmer fashion, I’ve got the high-level design done, but will implement from the bottom, most-detailed part up.

Gems

Gems are divided into two general classes, semi-precious stones and precious stones. Precious stones are ideally clear, even-colored (with some exceptions; some particular irregularities are very appealing), and often cut so they are faceted. Semi-precious stones are more common and are often opaque and/or have patterns or irregularities in their coloration that give them their appeal.

Some earlier editions of D&D had fairly complex rules for determining gem value, but this article is based more closely on the Pathfinder Roleplaying Game. This model identifies six grades of gems. Each grade has a different standard value, and it can be easiest to simply use the base values. There can also be some variation in the values, but not nearly as much as the earlier editions.

d20 Grade Name Standard Value Random Value Random Range
1-5 1 Least Semi-Precious 10 gp 5 gp + 2d4 gp 7-13 gp
6-10 2 Lesser Semi-Precious 50 gp 25 gp + 2d4 × 5 gp 35-65 gp
11-14 3 Semi-Precious 100 gp 50 gp + 2d4 × 10 gp 70-130 gp
15-17 4 Greater Semi-Precious 500 gp 250 gp + 2d4 × 50 gp 350-650 gp
18-19 5 Lesser Precious 1,000 gp 500 gp + 2d4 × 100 gp 700-1,300 gp
20 6 Greater Precious 5,000 gp 2,500 gp + 2d4 × 500 gp 3,500-6,500 gp

Both the standard value and the random value are workable. The standard value feels a little like funny-shaped coins (especially considering the recommendation to assume 50 gems weighs a pound) but it really is straightforward and easy to apply. The random value amounts to the same thing in the long run but has a little more texture, at the expense of a bit more work.

I’m going to take it a step further. Older editions actually described why the gem was worth more or less. I’d like to retain that.

A simple way is to use the dice of the random range to assign size and quality. This almost works, but I don’t see in the table how to have an “average medium-sized” gem. With four values per die you don’t have ‘average’ values on the individual dice, even though the two dice together have an integral average (mean) value.

However, it is easy to fake it using a pair of d10s. I initially considered applying these as “d5s” but ended up weighting the ranges differently. They still get added together to get the modifying value.

d10 Value Size Quality Alternate Value
<1 -3 Diminutive ? not yet named -3 + roll
1 -2 Tiny Flawed -2
2-3 -1 Small Poor -1
4-7 +0 Medium Average +0
8-9 +1 Large Good +1
10 +2 Huge Excellent +2
>10 +3 Gargantuan Flawless +2 + roll – 10

2016-10-26 I realized there’s really no reason these have to be capped at -3..+3 when the size or quality roll would be very far out of bounds. The difference in value is 10% per point (see below), so if you manage to get a size 10 quality 10 stone it’s still only worth three times normal. I provide an alternate value for those cases that gives an addition +-1 for each point the roll is outside the normal 1..10 range.

This gives a slightly wider range (from -2 to +2 on each die, assuming no modifiers, giving -4 to +4 in the final result instead of -3 to +3) but keeps pretty close to the same percentages for the same values. I show values outside the normal d10 die range because later articles will include modifiers to the rolls.

Value 2d4 Indexed 2d10
-6
-5
-4 1
-3 6.25 4
-2 12.50 12
-1 18.75 20
0 25.00 26
+1 18.75 20
+2 12.50 12
+3 6.25 4
+4 1
+5
+6

The values shown above adjust the market price of the gem by 10%. That is, a large (+1) excellent (+2) opal (greater semi-precious gem, base value 500 gp) would have a market price of 650 gp, while a small (-1) excellent (+2) opal would have a market price of 550 gp, and a tiny (-2) flawed (-2) opal would have a market price of 300 gp.

Despite using the normal size descriptors, I’m going to consider gems to be 100 per pound. I had originally thought to use 50 per pound, then I read that the Hope Diamond — which would likely count as a ‘huge gem’ under this scheme — is a touch over 9 grams in mass: 1/50 of a pound. As almost all gems are probably less than half this, I figured 1/100 pound each should be fine. (And if this causes problems with the encumbrance rules, the encumbrance rules aren’t where the problem is…)

I considered varying by size descriptor, but decided that if we don’t bother doing that for coins I’m certainly not going to bother for gems.

Now, just to see what it looks like in practice…

  • a medium [0] average [0] jade [100]: [100 gp]
  • a medium [0] good [+1] turquoise [10]: [11 gp]
  • a tiny [-2] poor [-1] moonstone [50]: [35 gp]
  • a large [+1] poor [-1] obsidian [10]: [10 gp]
  • a large [+1] average [0] aquamarine [500]: [550 gp]
  • a large [+1] poor [-1] topaz [500]: [500 gp]
  • a large [+1] average [0] carnelian [50]: [55 gp]
  • a medium [0] good [+1] jasper [50]: [55 gp]
  • a large [+1] average [0] ruby (blood red) [5000]: [5500 gp]
  • a tiny [-2] average [0] citrine [50]: [40 gp]
  • a huge [+2] average [0] aquamarine [500]: [600 gp]
  • a large [+1] excellent [+2] sapphire [1000]: [1300 gp]
  • a huge [+2] good [+1] spinel (red or green) [50]: [65 gp]
  • a small [-1] flawed [-2] quartz (milky, rose, or smoky) [50]: [35 gp]
  • a medium [0] good [+1] spinel (red or green) [50]: [55 gp]
  • a large [+1] excellent [+2] pearl (black) [500]: [650 gp]
  • a medium [0] excellent [+2] diamond (fancy) [5000]: [6000 gp]
  • a huge [+2] average [0] amber [100]: [120 gp]
  • a small [-1] average [0] pearl (saltwater) [100]: [90 gp]
  • a medium [0] average [0] topaz [500]: [500 gp]
  • a small [-1] poor [-1] coral [100]: [80 gp]
  • a tiny [-2] excellent [+2] sapphire [1000]: [1000 gp]
  • a small [-1] excellent [+2] ruby [1000]: [1100 gp]
  • a small [-1] average [0] topaz [500]: [450 gp]
  • a medium [0] average [0] topaz [500]: [500 gp]
  • a medium [0] flawed [-2] jet [100]: [80 gp]
  • a small [-1] flawed [-2] turquoise [10]: [7 gp]
  • a tiny [-2] average [0] jet [100]: [80 gp]
  • a medium [0] good [+1] ruby [1000]: [1100 gp]
  • a large [+1] good [+1] pearl (black) [500]: [600 gp]
  • a medium [0] good [+1] malachite [10]: [11 gp]
  • a medium [0] average [0] amethyst [100]: [100 gp]
  • a medium [0] poor [-1] jet [100]: [90 gp]
  • a small [-1] average [0] pyrite [10]: [9 gp]
  • a large [+1] flawed [-2] jasper [50]: [45 gp]
  • a medium [0] good [+1] onyx [50]: [55 gp]
  • a large [+1] average [0] jade [100]: [110 gp]
  • a large [+1] good [+1] obsidian [10]: [12 gp]
  • a medium [0] flawed [-2] peridot [50]: [40 gp]
  • a large [+1] average [0] tigereye [10]: [11 gp]
  • a large [+1] average [0] pearl (black) [500]: [550 gp]
  • a tiny [-2] good [+1] onyx [50]: [45 gp]
  • a huge [+2] average [0] shell [10]: [12 gp]
  • a medium [0] poor [-1] coral [100]: [90 gp]
  • a medium [0] excellent [+2] pyrite [10]: [12 gp]
  • a medium [0] poor [-1] jade [100]: [90 gp]
  • a medium [0] flawed [-2] sardonyx [50]: [40 gp]
  • a small [-1] poor [-1] carnelian [50]: [40 gp]
  • a small [-1] poor [-1] opal [500]: [400 gp]
  • a small [-1] average [0] quartz (rock crystal) [10]: [9 gp]
  • a huge [+2] average [0] lapis lazuli [10]: [12 gp]
  • a medium [0] good [+1] rhodochrosite [10]: [11 gp]
  • a small [-1] good [+1] amethyst [100]: [100 gp]
  • a small [-1] average [0] opal [500]: [450 gp]
  • a large [+1] flawed [-2] quartz (milky, rose, or smoky) [50]: [45 gp]
  • a medium [0] average [0] pearl (irregular freshwater) [10]: [10 gp]
  • a medium [0] flawed [-2] spinel (red or green) [50]: [40 gp]
  • a large [+1] average [0] carnelian [50]: [55 gp]
  • a tiny [-2] poor [-1] diamond [1000]: [700 gp]
  • a medium [0] average [0] pearl (black) [500]: [500 gp]
  • a tiny [-2] good [+1] citrine [50]: [45 gp]
  • a medium [0] poor [-1] ivory [50]: [45 gp]
  • a medium [0] average [0] sardonyx [50]: [50 gp]
  • a medium [0] excellent [+2] opal [500]: [600 gp]
  • a large [+1] good [+1] shell [10]: [12 gp]
  • a large [+1] average [0] shell [10]: [11 gp]
  • a small [-1] average [0] malachite [10]: [9 gp]
  • a small [-1] excellent [+2] rhodochrosite [10]: [11 gp]
  • a large [+1] flawed [-2] coral [100]: [90 gp]
  • a large [+1] average [0] chrysoberyl [100]: [110 gp]
  • a medium [0] average [0] tourmaline [100]: [100 gp]
  • a large [+1] good [+1] spinel (red or green) [50]: [60 gp]
  • a huge [+2] average [0] pearl (saltwater) [100]: [120 gp]
  • a medium [0] good [+1] sardonyx [50]: [55 gp]
  • a medium [0] flawed [-2] pearl (black) [500]: [400 gp]
  • a large [+1] flawed [-2] obsidian [10]: [9 gp]
  • a large [+1] average [0] aquamarine [500]: [550 gp]
  • a large [+1] average [0] topaz [500]: [550 gp]
  • a tiny [-2] poor [-1] moonstone [50]: [35 gp]
  • a large [+1] average [0] opal [500]: [550 gp]
  • a huge [+2] average [0] emerald (brilliant green) [5000]: [6000 gp]
  • a medium [0] poor [-1] alabaster [10]: [9 gp]
  • a large [+1] poor [-1] onyx [50]: [50 gp]
  • a medium [0] average [0] pyrite [10]: [10 gp]
  • a medium [0] poor [-1] opal [500]: [450 gp]
  • a tiny [-2] average [0] citrine [50]: [40 gp]
  • a medium [0] good [+1] tourmaline [100]: [110 gp]
  • a huge [+2] poor [-1] pearl (black) [500]: [550 gp]
  • a medium [0] poor [-1] jet [100]: [90 gp]
  • a medium [0] average [0] diamond [1000]: [1000 gp]
  • a medium [0] excellent [+2] opal [500]: [600 gp]
  • a medium [0] flawed [-2] pyrite [10]: [8 gp]
  • a medium [0] poor [-1] spinel (deep blue) [100]: [90 gp]
  • a medium [0] poor [-1] pearl (saltwater) [100]: [90 gp]
  • a large [+1] average [0] shell [10]: [11 gp]
  • a medium [0] good [+1] azurite [10]: [11 gp]
  • a medium [0] good [+1] pearl (irregular freshwater) [10]: [11 gp]
  • a small [-1] good [+1] ruby [1000]: [1000 gp]
  • a tiny [-2] average [0] jet [100]: [80 gp]
  • a medium [0] average [0] opal [500]: [500 gp]

I used a weighted table of grades (1-5 grade 1, 6-10 grade 2, 11-14 grade 3, 15-17 grade 4, 18-19 grade 5, 20 grade 6) and I’m showing the input values so I can double check… basic verification.

So far, so good. More to come.

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  1. on June 9, 2016 at 12:56 pm