[DF 8] On Gemstones and Carats
 

Honestly, I know nothing about precious gemstones. Not really interested in them other than as treasure for role-playing games. Reading over Dungeon Fantasy 8 -- and I love DF 8! -- I wondered how many carats I should make an astounding, jaw-dropping gem of the size common in cinema and high-fantasy fiction, like the ones found in the hands an eyes of golden idles and such. For example, the statue's eye on the cover of the AD&D Player's Handbook or the red gem Abu tries to steal in Disney's Aladdin.

How many carats would a golf-ball-sized emerald, amethyst, ruby or diamond be? Google tells me golf balls are about 42.67 millimeters in diameter.

How about a truly-fantastic baseball-sized emerald, amethyst, ruby or diamond? Again, Google tells me they are 73–76 millimeters in diameter.

Thanks!

Re: [DF 8] On Gemstones and Carats
 

Per Wikipedia, a carat is 200mg, and a diamond's density is 3.5 grams per cubic centimeter. your golf ball comes in at 40.7 cc's, so a diamond that size would weigh 142 grams – 710 carats, about 5 ounces avoirdupois.

Re: [DF 8] On Gemstones and Carats
 

One carat equals 0.2 grams, so just figure out how much the gemstone weighs and convert to carats. For example, Diamond has a density of around 3.5 grams per cubic centimeter, so a sphere 4.3 cm across (roughly 41.6 cm^3) masses 145 g, hence 725 carats. Clearly, such massive stones are ludicrously rare and valuable; DF8 gives it a price tag of over $21 million.

Re: [DF 8] On Gemstones and Carats
 

As the price was already answered one thing to consider if you really want that size without bank rolling the PCs for life.
That is more then a Kings ransom and likely searching for a buyer would be a significant adventure on its own. Its perfectly reasonable to say no buyer exists in fact. They may chop it down to smaller pieces but would lose a lot of the value and still may have troubles.

Re: [DF 8] On Gemstones and Carats
 

For comparison, the largest cut diamond in the world is the Golden Jubilee Diamond at 545.67 carats. It had an uncut weight of 755.5 carats.

The largest uncut diamond ever was the Cullinan Diamond, at 3106.75 carats. It was cut into 105 smaller gems.

Re: [DF 8] On Gemstones and Carats
 

There's no way I can do that math.

Amethyst has a density of 2.65 g/cm^3. How many carats would a golf-ball-sized one be?

Looks like rubies have the same density as diamonds, so I know that answer.


I centered a whole play-by-post campaign on trying to get rid of a large gem once.

In the end, they sold the priceless, magical gem for something like $1,000 split four ways -- which was a substantial sum less than they agreed to steal it for!

It didn't save them. At least one PC was murdered over it.

Re: [DF 8] On Gemstones and Carats
 

Diomedes' post included the volume of the golf ball (40.7 cc), which multiplied by the density immediately gives ~108 gram. Or, simply putting "40.7*2.65 gram in carats" into google, you get the conversion to 539.27500 carats.

Re: [DF 8] On Gemstones and Carats
 

Thanks!

....

Re: [DF 8] On Gemstones and Carats
 

The math itself isn't actually too hard. You just need the formula for a sphere: volume = (4/3) * pi * radius^3. Just plug in the radius in centimeters and it'll give you a volume in cubic centimeters, multiply by density (g/cc) to get grams, then multiply by 5 for carats.

Re: [DF 8] On Gemstones and Carats
 

Getting technical (and realistic) - cutting up a flawless diamond will almost certainly decrease its value, but cutting up one with a flaw may actually increase it. A competent cutter will get a whole load of smaller but flawless stones out of the cut. Also, if the stone is stolen and the rightful owners can and will assert their rights, cutting it up should make it unidentifiable; would you rather have five million you can't realise or a million you can?

Though modern-style gem-cutting is mostly a post-Renaissance thing anyway, so those who insist on making their fantasy worlds "realistic" medieval-style settings should really be ignoring this stuff.

And in any case, once you get up to insane golfball sizes for stones, the question of flaws and such becomes a bit moot. You're talking sheer uniqueness there, and the value of the stone is what it will bring. Which is probably three or four plots, several rumours about curses, multiple murders, and a large moral Aesop by the end of the campaign.

(I'm also remembering the nice story of the guy who found a very large gold nugget a few years back, and determined that it was the 23rd largest ever discovered. He then discovered that the 22 bigger had all been melted down for the, you know, gold - so he actually had the largest extant nugget. So he eBayed it, and got several times its metal content value from a Las Vegas casino.)

Re: [DF 8] On Gemstones and Carats
 

Using DF8 gives you a 1/36 chance of BIGGER!.

So, how rare do you want the gem to be?

Odds of being an N iteration of BIGGER! are 1/(36^N)

To do the math for you:
1: 32
2: 1,024
3: 32,768
4: 1,048,576
5: 33,554,432
6: 1,073,741,824
7: 34,359,738,368

So, to put it in the range of 1 bigger makes it as big as one in 32 gemstones. 2 biggers makes it one in a thousand (or so). A 1-in-a-million gem is in the 4 biggers range. 6 biggers is probably the only gem of its kind in the world. More than that is just ridiculous. This involves no reality-checking. Just crunching numbers from DF8 to see the odds. Also note that there are great overlaps in the size ranges, but as you roll more dice you'll get to a more average result.

P.S. It hurts me to write the word "biggers"

Re: [DF 8] On Gemstones and Carats
 

Nah, you're just looking at the biggest gem in the inner planes, then the biggest gem in the inner and outer planes, and then probably "the heart of the First Dragon/Creator God/Abyss".

On the other side of things, there's "gem stones" as the term is used in jewelery, which is to say "pretty rocks", which can include some that get VERY big.

Quartz: "Well-formed crystals may reach several meters in length and weigh as much as 1,400 pounds (640 kg)."

Jade: "The world's largest pure gemstone quality jade named "Polar Pride" was discovered in British Columbia in the vicinity of Dease Lake. It weighed 18 tones..."

Hematite: "The most spectacular large crystals of hematite--flat plates 6 in. (15 cm) or more across--have been found in metamorphosed Brazilian sediments."

Re: [DF 8] On Gemstones and Carats
 

For stones that large, I suspect that the Carat-based pricing presented in DF8 breaks down. A single Jade boulder weighing 18 tons (90 million carats) would be valued at $162 Quadrillion, which is over 2500 times the GDP of the entire planet. Even a 1400 pound quartz comes in at over $150 Trillion. At some point the pricing scheme must drop the mass^2 component, and plateau at a fixed price per kilo.

Re: [DF 8] On Gemstones and Carats
 

There is a cave in Mexico with impressive gypsum crystals.

Re: [DF 8] On Gemstones and Carats
 

It currently doesn't, despite having a whole bunch of decorative stones and not-really-stone materials that appear in single pieces significantly larger than traditional "gemstones".

Which is probably a decent enough abstraction for DF - it's not like the value per carat isn't completely made up as it is. But quartz, jade, jet, coral, etc and any of the bulk iron or copper ores should (in a more accuracy-concerned game) just be a fixed per pound measurement (SJG measures by the lb, as much as I'd prefer kg).

My point was more "Or the giant stone in the idols eye could be Chalcondy" - still seriously worth it as a giant lump of reasonably expensive decorative material, but not quite so economy imploding as a giant ruby.

Re: [DF 8] On Gemstones and Carats
 

The based on square of carats is largely a function of the rarity of large unflawed stone. For stones where flaws are invisible or irrelevant, it doesn't make sense.

Re: [DF 8] On Gemstones and Carats
 

In real life Earth gemstones in the Middle Ages were polished not cut. And diamonds were not popular due to their lack of color. It was not until the modern cutting methods that created a play of colors from the interplay of light between the facets that diamonds became popular; that and a great publicity campaign by DeBeers.
In the Middle Ages the pricing would have been different than the modern method. It was: What does the customer look like they will spend? Even today there is a strong element of "An item of jewelry is worth what you think it is worth." in all transactions. Back then jewelry and gems were a status indicator and the bigger the rock, the higher your status was presumed to be.
Also, bear in mind that the designation of gems was a lot looser than present day. Green gems were lumped as emeralds but today a distinction would be made between emeralds and other green gems.
Fashon and style made a huge difference in price so you can get away with charging whatever you want when the players buy and giving whatever you want to give when they sell. They do not have to agree with what is offered but there would be, historically, no fixed method of determining a value independant of that.

Re: [DF 8] On Gemstones and Carats
 

So give them a 710 carat zircon. :)

Re: [DF 8] On Gemstones and Carats
 

Several years ago, there was an exhibition in Memphis, TN of artifacts and possessions of the Ottoman Sultans, including the legendary Topkapi Dagger. There were some other gemstones and jewelry that on display that belonged to the earlier sultans, and you could see the difference in gem technology vividly on display. The older items were polished gems, not cut or faceted, they looked like what they were, pretty colored rocks, rather than crystalline translucent sparklers. The newer items, made more recently with more advanced techniques, looked more like what we think of as 'gems and jewels'.

Re: [DF 8] On Gemstones and Carats
 

And going the other way, rubies and sapphires were split up, even though they are the same kind of rock with different impurities. Same with beryl, aquamarine, and emerald.

And of course, several gem "stones" are not really stones in the truest sense. Pearl, jet, amber, opal, etc.

Re: [DF 8] On Gemstones and Carats
 

First, a disclaimer: I am not an expert on gemstones.

I agree with the basic point, but have to disagree with a detail. Gemstones have been cut for thousands of years. Faceted stones came in sometimes around the 14th century, and more modern and brilliant cuts came in sometime around the mid to late 1400s and later.

Also value in modern day is largely based on the four Cs: Cut, Clarity, Color, and Carat. But that may be more detail that the OP wants.

Re: [DF 8] On Gemstones and Carats
 

I understand you to be referring to the organic origin of these items, but still, jet, amber and opal are stones. Jet is a lignite, which means it will burn, because of its fossil origin, and amber is fossilized sap. I don't know why you wouldn't call opal a stone -- it's amorphous, but it's silica, not organic. Are you thinking of a specific definition?

You're quite right about the origins distinguishing some of them, though. In a setting where ridiculously large minerals are available in quantity, it may well be the case that the highest esteem is given to pearl, coral, amber, possibly exotic woods and fine furs, rather than pretty rocks.

Re: [DF 8] On Gemstones and Carats
 

I suppose I was actually thinking of the definition of mineral, rather than stone.

Re: [DF 8] On Gemstones and Carats
 

Crystal perhaps? I don't think any of those are crystals at all, but then I don't think any of the opaque stones are crystals except some forms of hematite... which is "just" an iron ore and fundementally not that exciting unless you really like the look. I prefer it over just about all the so-called precious gem stones, but then I don't really like yellow gold that much and I'm sort of iffy about silver so I'm clearly in the minority.

Pewter, wrought iron, bronze/brass, copper, or steel and hematite or jasper - I'm clearly easy to shop for. Which just goes to show that decorative items are priced mostly on supply and demand.

Re: [DF 8] On Gemstones and Carats
 

Pewter is awesome, but still quite expensive (nowhere near the cost of silver and gold obviously, but even so). Wrought iron can be nice, but only because its common form these days is in old fashioned aesthetics. Same goes for bronze brass and copper, they're quite rare these days for made goods so tend to stand out a little more, plus they polish up really well.

But steel?? I can't see it sorry, okay I'd not turn down a fine steel sword, but its as common as common metals gets these days and hardly ever used in "art" because of it (unless its just the frame with something else around it). I can understand titanium, a personal love of mine, because of its other properties... but steel is just so regular now.

*shrug* I guess this does just go to show that everyone's tastes are different, and whilst some people want natural diamonds and non-farmed pearls... I'm quite content with base metals and synthetics. Although one day I'll get me a hunk of meteorite or have some inlaid into a ring, because its BEEN IN SPACE and therefore automatically awesome.

Re: [DF 8] On Gemstones and Carats
 

Or put another way; bling (in any century) is less about the buyers taste and more about how valuable an item looks when worn.

Re: [DF 8] On Gemstones and Carats
 

That's actually half the attraction - it's a practical, hard-wearing metal with a lot of cultural associations with tools and weaponry. EDIT: the "classess" or "tradesman" associations are important as well.

I confess to a deep personal weakness for punk aesthetics (which fades into "goth" and "metal"), and even some of the stupider-looking heavy-metal excesses. Which is funny, because I'm the first to admit it's stupid looking.

But it has to be steel - nobody's going to take any studs or spikes seriously if they're gold or even bronze; it has to be steel (possibly chromed) or it looses the implications of "practical application", which means in turn it looses the impact as a threat display, which means you're not punk you're just a poser.

Re: [DF 8] On Gemstones and Carats
 

Point. However I'd still raise the game and go with titanium, nothing gets more practical and hard-wearing that that! You can ever colour it without chroming so it'll keep any choice colour alterations from wearing off. But at least I can see the wavelength your on now, so I'll stop sidetracking the thread...

Re: [DF 8] On Gemstones and Carats
 

^
~3.2 million carats! Worth ~$150 trillion according to DF8.

Not only is this one a powerstone, but it's enchanted as well. Even the shard in his hand is pretty big for a powerstone.

Re: [DF 8] On Gemstones and Carats
 

There was an article in Pyramid v2, about the value of precious and semi-precious gemstones. For precious gemstones, the carat weight was lifted to the 2nd power, possible with a linear component too (IIRC similar to the Powerstone rules for 3E and/or 4E), and that seemed sensible to me.

For semi-precious stones and materials, such as amber, the rule was that you lfited the carat weight to the power of 1.01. That seemed kinda sensible to me, since it seems to me that one lump of amber weighing 50 grams should be worth somewhat more than two lumps of amber each at 25 grams.

But then I tried the formula with some actual numbers, and it turns out that a 1 kilogram semi-precious stone (5000 carats) is only worth about 10% more than the same mass distributed amoung thousands of smaller stones (weighting 1-2 carats each).

So if you use that formula, it's not worth the bother. I do maintain that larger lumps of amber should be worth somewhat disproportionately more, but I haven't needed to solve the problem yet, so I don't know what kind of power to use, 1.05 or 1.1, to produce results that seem reasonable. Or that are even worth the bother. The Pyramid formula seems like a waste of time, performing an arithmetical calculation - even if it is a very simple one - for really no gain at all.

Re: [DF 8] On Gemstones and Carats
 

It's very possible to create a "cheat sheet", using Excel or Calc, for a variety of standard gemstone types and sizes. It's just not something I've gotten around to yet, in part because gemcutting would be anachronistic in my primary setting.

Re: [DF 8] On Gemstones and Carats
 

Is it really that large pieces of amber are worth more, or that the cost of adding the shaping and polishing to make it gem quality is largely independent of size (big ones need more work, small ones need more intricate work)? On the other hand, a large piece suitable for making a large "gem" is likely to be more rare than a large piece only suitable for making a lot of little gems, but I don't know enough about amber to say much about it.

Re: [DF 8] On Gemstones and Carats
 

I'm thinking necklages of merely polished amber beads, as the "baseline item".

Re: [DF 8] On Gemstones and Carats
 

Compared to steel titanium is ludicrously expensive and for the purposes of a DF game unknown on Earth until 1791. (And it took even longer to be easily refined and to find a practical use.)

Re: [DF 8] On Gemstones and Carats
 

I'm by far no expert on the subject, but "flaws" in amber are unusual in the way they're handled as some prefer that aesthetic. Whilst inclusions can make a piece significantly more expensive, subject to number/ size/ commonality and "pleasing form".

A tiny piece of amber with a fly in it for example will be worth more than the norm for that size, but not massively so - but a moderately sized clear piece with a large and rare specimen positioned centrally and in an easy to identify shape (so not all on top of itself) is worth multiples of cost more! I know, I've tried to buy some in the past.

So even though its a relatively inexpensive "gem" for the most part, there are factors that can really affect the cost beyond size/clarity.

Oh obviously! I'd never get a studded jacket made with titanium studs unless I suddenly gained more money than my current level of sense (so lots) or I suddenly gained some sort of superpowers and a sig-gear motorbike... like Ghost Rider or something. It doesn't stop the metal being cooler, it's just often less justifiable.

In a world where dwarves have mastered the art of making titanium, I'm sure they'd be dwarven kings coated in the stuff whilst especially wealthy Dire Boar war-riders would stud leather jackets with it to look extra badass.

Re: [DF 8] On Gemstones and Carats
 

That's largely the role of "mithril."

Re: [DF 8] On Gemstones and Carats
 

Titanium by any other name is still just as cool.

Re: [DF 8] On Gemstones and Carats
 

Just made one, specifically aimed at the OP :D It uses the exact rules from DF8, even though they're questionable for semiprecious gems.

Can't use it in GDocs as GDocs does not support drop down boxes and images, so you'll need to download it and open it in Excel to use it;

https://docs.google.com/open?id=0B9v...19sRmJGZzk4STQ

To download go to the GDocs file menu and pick Download. :D

Usage: Click on the orange box next to Gem to pick your gem type from the dropdown list.
Click on the orange box next to Shape to pick the shape of your gem (see the pictures at the bottom of the sheet for examples of everything except Polished Sphere to see what I mean).
Enter the Diameter of your gem and pick your units from the dropdown box (supports Inches and CM)

Sheet gives you volume, weight in ounces, grams, and carats, and gives you the value according to DF8.

I'm working on an alternate to the gems table, splitting it up into precious and semi-precious and calculating the value of each differently. This version has a separate gem quality table, giving you quality ranges from Poor to Flawless (multiplies cost from 1/5x to 5x that indicated by weight).

Re: [DF 8] On Gemstones and Carats
 

Google Docs may not support importing those from Excel, but it definitely supports drop-down boxes and images.

EDIT: Did a quick conversion to a native Google Spreadsheet of the working part of Bruno's spreadsheet (there's more in Bruno's that doesn't connect to the actual calculation part, and that's not included) -- minus the images for now.

Re: [DF 8] On Gemstones and Carats
 

That's a neat spreadsheet, Bruno. Many thanks. Makes it much easier to visualize what the gems actually look like for those of us who never deal in carats.

Re: [DF 8] On Gemstones and Carats
 

If you offer this in an attempt to quench my deep, dark hatred for you...

...it worked! XD

Now, I only have to get MS Office. I saved it in my GURPS folder for one day when I finally get it.

Thanks!!! :D

Re: [DF 8] On Gemstones and Carats
 

I added this in an edit to my earlier post, but I'll risk the redundancy for the greater visibility of a new post: I just posted a quick conversion of Bruno's sheet in native Google Spreadsheet form, so you can use it online without Office.

Re: [DF 8] On Gemstones and Carats
 

What is the DF8 rule for semiprecious gems? I've forgotten. Cost linear with mass?

Re: [DF 8] On Gemstones and Carats
 

Can't Libre Office open the file?

Re: [DF 8] On Gemstones and Carats
 

Of course DF gems are likely measured in ounces. if not pounds...

Re: [DF 8] On Gemstones and Carats
 

Thanks!

Quick question in case I don't figure it out right away, how does one edit the fields? I tried clicking, double-clicking and right-clicking...

I can edit the carats field, right?

Either way, the spreadsheet looks great!

DF8: "The value of a gem in $ is (C2 + 4 x C) x V, where C is the weight of the gem in carats and V is the Value modifier for the gemstone."

Low-Tech: "Gemstones have a nominal price given by: Price = ($1 x C2 + $4 x C) x V"

Re: [DF 8] On Gemstones and Carats
 

I'm using Firefox 3.6, which apparently isn't fully compatible with Google Docs. Upgrading to Chrome should make it work (though in my case my OS is too old to allow that). You can also try Open Office, which seems to open the .xls file, though some options may not be compatible (there are some #VALUE fields on the third sheet).

Re: [DF 8] On Gemstones and Carats
 

Its set to view-only (so anyone using it doesn't edit the original) so you need to make a copy of the spreadsheet in Docs to work with. Once you do that, the shaded areas are where you should edit (blue are drop downs, the diameter is a direct entry.)

The other cells are formula driven (including carats, which is one of the weight measures), which is the same way Bruno's works -- the intended use is entering the diameter and the weight is calculated from that, the shape, and the kind of gem.

There's no actual protection on fields, except the data validation on the shaded fields, but changing other things will break formulas, so you should only do that if you are reworking the form.

Re: [DF 8] On Gemstones and Carats
 

Awesome! If you can't tell, I'm not really familiar with Google Spreadsheet :D

Aren't I sneaky?

DF8 doesn't have a separate pricing system for semiprecious, and doesn't actually make a distinction. Which makes about as much sense as anything else in a fantasy world and it's not like the precious gem numbers are particularly historical (most valuable is diamons), but it still annoys me.

The one I did, and cmdicely's conversion it looks like, both calculate carats from gem type (which references real world gem specific gravity) and volume (based on diameter at widest point and some generic sizes/shapes).

You can type over the formula in the carats field in your copy and just either don't save it, or "Undo" before saving to get the formula back. Or save a second copy for typing the carats number in by hand, which is probably safer now that I think about it.

As DF8 doesn't give a mouses fart about whether the gems are cut, shaped, opaque, sparkly, flawed, or up a dragons nose at the time, there is no cost adjustment for the various cuts/shapes included other than to account for volume differences.

I'm making a slightly fussier spreadsheet that

A) lists semi-precious (based on modern definitions of semi-precious) separately from precious and uses a different value calculation (C^1.02 * V which seems "good enough")

and B) introduces an (optional) roll for quality, which will abstractly cover the whole range of funny/perfect colour, stylish/tacky cut, valuable amber inclusion vs terrible inclusion in another type, flaws, etc etc.

Everything is coming with DF8 compatible table rolls, with the goal of being a drop in replacement. I've had to add a couple more semi-precious stones to make those table rolls work out :P

Once I'm happy with it, I'll figure out how the drop-downs work in GDocs and put it up :D

Re: [DF 8] On Gemstones and Carats
 

BTW: cmdicely, your version of the spreadsheet has unfortunately hashed up the inches/cm - you're using the conversion between linear inches and linear cm, but the actual units involved are CUBIC inches vs CUBIC cm. Your value on the units sheet for inches needs to be 2.54^3 or 16.387064

Re: [DF 8] On Gemstones and Carats
 

Oh, bother. Should be fixed now. (Actually fixed the formula on the main page.)

Re: [DF 8] On Gemstones and Carats
 

Eheh, that works too.

Re: [DF 8] On Gemstones and Carats
 

How about a new thread for these spreadsheets? There are probably people who would be interested in them, but wouldn't look at a tread on measuring gemstones.