The Crown Jewels are so shiny...so impossibly shiny (and very worth seeing!). Gems of that calibre aside, I was also thinking of things like "a ruby fished from the heart of a volcano, and impregnated with the raw essence of Ignem" would also qualify as priceless? Acquire only by adventure and such.
RL rubies, would not be found in the heart of a volcano- even within mythic Europe where gems are assumed to breed under the earth in conformity with medieval lore, finding a gem in the heart of a volcano would be an exceptional event.
That being said while the event in question would likely have a significant impact on the magical qualities of the gem, I don't see how it would impact the gem quality of the gem- unless of course it is a faerie gem where it's external properties are a mirror of the internal mystical qualities, in which case any faerie gem containing a rook or more of vis is likely to be categorized as priceless.
As mentined, all stones have absolute clasifications that go back to Ancient Greece (I do need to check my facts, but I am pretty sure that is the source). It does not matter how rare or magical the stone is or what actual vaule it has.
Based on my research, in the ancient world there were five cardinal (precious) gems: ruby, diamond, emerald, sapphire, and amethyst. Although amethyst was later classified as a semi-precious gem, leaving just the REDS precious, back in the ancient world (at least the ancient Western world), amethyst was considered a precious gem.
this page gives a list of 24 'cardinal' gemstones, the one considered most likely to be a 5 precious stone is Opal, unless you are getting your information from wikkipedia or I suspect certain pagan sites where amethyst is chosen because it is purple and thus symbolizes 'spirit' as the fifth element. Amemthyst was named in ancient Greece as a cure for drunkenness, which to me suggests it was a fairly common stone to have such a banal usage, and it is ultimately a form of quartz, which is simply a plentiful crystal, in addition to which quartz crystal have been alterable through fire treatment back to 4000 BC, which means amethyst could be made from other forms of quartz, which would definitely prevent it from being considered a precious stone.
Setting aside wikepedia and the many admittedly unreliable websites on the Internet, there is still a good deal of support for amethyst having once (prior to the 19th Century) been a precious gem. I have not, as you suspected, gone to any pagan sites as what they say has no scientific foundation whatsoever. What I have found from more reputable sources is that amethyst is the rarest form of quartz, and was quite rare up until the 19th century.
Gems and Precious Stones: With Descriptions of Their Distinctive Properties ..., by Henry G. Smith, page 59, states that as late as the middle of the seventeenth century, a specimen of amethyst was considered to be worth as much as a diamond of equal weight; but since that time, perhaps owing to its being found in large quantities in Brazil, America, and elsewhere, the value has much depreciated.
Gemstones: Species & Varieties, by Charleen Kiefer, page 51, notes that amethyst was considered rare and precious in the Old World, until large deposits were found in Brazil.
Rockhounding New England: A Guide to 100 of the Region's Best Rockhounding Sites, by Peter Cristofono, page 70, notes that amethyst was once considered one of the cardinal gemstones, but lost its value after extensive deposits were discovered in Brazil.
The Gem Encyclopedia of the Gemological Institute of America (GIA) notes that amethyst was as expensive as ruby and emerald until the 19th Century, when Brazil’s large deposits were discovered. (gia.edu/amethyst)
Minerals.net notes that amethyst was once highly regarded among the precious gemstones like Ruby and Emerald, but discoveries of huge Amethyst deposits since the 1800's have made Amethyst fairly inexpensive and very obtainable. (minerals.net/gemstone/amethyst_gemstone.aspx)
Furthermore, the site you referenced notes:
Historically, amethyst was considered to be one of the five "cardinal gems," which also included diamond, emerald, ruby and blue sapphire, yet today amethyst is both abundant, and inexpensive, placing it more appropriately in the category of "semiprecious." However, a bicolored variety of amethyst called ametrine is both rare and expensive, which would certainly place it in the category of "precious." The gem known as Tsavorite is an extremely rare and valuable variety of an otherwise ordinary gem known as grossularite, or grossular garnet.
So I'm looking to make Thomas' familiar and I wanted to get the troupe's imput. Per the rules, since he's a 'Magic Spirit Companion' (flaw) who was then enchanted as a familiar (Spirit Familiar Virtue), he's going to be built as an Autumn Character (720xp) with a Might of 20.
I was leaning towards the ghost being either an old Mercurian Priest or a Priest of Pluto (my personal favorite of the two). However, if you've got a really cool concept, by all means, I'd love to hear it!
Once the core concept is down, I'm also curious as to what folks come up with as suggestions for powers etc.
Final question, familiars can learn Magic Theory right? Not trying to give it a 10 in it or anything, but if it's been helping Thomas out in the lab for years at the very least it'll have a rudimentary understanding, even if its never cracked a book (yay exposure xp!).
Funny fact! We actually have a local Priest of Pluto ghost - the recently identified (in the just finished "Mr Spooky Ch3" thread) Camillus Aurelius. So, that's a thing. Plot hook?
Oh really now? Time to go read said threat very carefully! Well I'm liking that idea even more now!
Typically for familiars, Marko allows you to choose on a sliding scale:
Might 5, Autumn Character
Might 10, Summer Character
Might 15, Spring Character.
To the best of my knowledge he hasn't allowed any 20 might familiars.
My next magus in the saga (whenever that happens) is going to be haunted by the ghost of an old Mercurian priest ancestor. So I think it's a cool concept.[sup]1[/sup]
Where do you figure you picked the old fellow up? And how/why did you bind him? I think the story of how he came to be your spirit familiar would shape who you want him to have been.
Another issue is explaining why a ghost that old wouldn't be able to reveal lost secrets. The plan for my magus is to say that over the ages memory of the details of Mercurian rituals has faded from the ghost's memory. He'll have a strong personality and strong opinions, but no lost knowledge. That's something you'd have to address, I should think, in order to keep balance in the world.
[sup]1[/sup] - but see my comment on your character thread about whether Mystery Virtues like Spirit Familiar are appropriate to be selected as starting Virtues.
Indeed, however look at this bit in the House Rules section on Familiars
Glad you approve! I had similar thoughts about loss of memory etc. However another option is simply, the Cult/Hermetics already know and or have integrated what the ghost knows. So some combination of the two? Like I said, I was leaning towards a Priest of Pluto. My thoughts being, he went crypt robbing... err I mean exploring for the cult, sometime during his apprenticeship and encountered the ghost. The two got to talking, the ghost took a liking to the very polite (scared shitless), respectful young magus and decided to accompany him.
As for the comment in the other thread (it keeps getting eaten by the forums it looks like), take a look at Cabal Legacy on page 20 of TMRE, it allows me to do just that. The idea being, he's been 'raised' as it were, inside the Mystery Cult, as opposed to joining later.
Ah, I hadn't noticed that. It's another of those flaws that looks more like an advantage than a disadvantage.
Though I'm still not sure how "most magi associate him with the Mystery" or "when a magus with Cabal Legacy speaks, magi often think he speaks for the entire cabal," as the Flaw says, when you keep your membership hidden.
Story flaws can be like that sometimes. Well, as you mentioned your reluctance to associate with Necromancers before, it could easily be that folks (rightfully) assume that he's a member and treat him as such (assuming of course they even know about the cabal), despite not having any proof. The House wouldn't care, as long as he keeps taking orders and doing his job, but others might, especially the more devout ones, and others might be interested in what he can do (for them)!
It's a story flaw, it leads to... stories. That's what's important yeah?
if you look here it explains that there really was no idea of a precious gem vs semi-precious in the middle ages, and if there were what those would be would have shifted wildly over time, but canonically this is not the case for Mythic Europe where the stones have been fixed since at least Ancient Greece and they are intrinsic properties. Also these values reflected other mystical attributes, and one certainly has to admit that the number 4 is of a certain significance within mythic Europe. If we want to go outside the standard 4 recognized today there is not one stone but nearly a score to choose from as potential other precious stones, and amethyst is but one of these. I would argue that both opal and pearl (despite not really being a stone) are both stronger contenders. Also even today depending on quality and the 4 Cs a simple rose quartz can be more valuable than an emerald (I at one point actually owned an emerald whose qualities put it in that category), so the issue is not one of price.
Now we could have 4 precious stones and stick with REDS, we could go with 5, 10 (one for each form) 15 (one for each art), or other traditional mystical numbers like 7, 12 or 13.
Especially for Guiverna. She loves it when people give her nice things. The nicer the better.
I'm not above blatant bribery... err I mean giving gifts to my sodales.
Please have patience everyone. I will be able to post lots and lots tomorrow.
Can Gunnvara be the redcap in back to Bellaquin?
I think Frederika's world view is begining to infect how I interpret everything that happens in this game. And because of that, I'm beginning (referencing the Back to Bellaquin thread) to seriously dislike Valgravian... 
At this point, I think Rika could rant for a good page on why he's a stuck-up, sanctimonious muck-raker. And how dare he even insinuate that Frederika would even possibly be involved in petty theft* when it's clearly his own incompetence that has lead to his missing articles!
*not to necessarily say Erika wouldn't involve herself in petty theft (with all the appropriate justifications) - just that she would resent the mere notion that she would be involved in something so base when she isn't actually involved at all. Have I mentioned that I enjoy how capital-P Proud she is?