UPDATE:
Looks like this scavenger hunt was already started by the
Molten rock mod people, who have done some spectacular work so far. I think it's best to take this discussion over there.
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I ran into the magma safe mechanism problem. What a pain. The only stone with a high enough melting point to resist magma is bauxite. Unfortunately, Bauxite is literally rarer than gold in the game. This has become a real problem for me because I'm playing Goblins, and can't order the stuff in. But it an issue which I know has bitten a lot of people.
There are various suggestions on the modding front, such as adding [ANY_USE] tags for iron, etc. However, I'd like to suggest a better solution which is both reasonable and won't adversely affect gameplay.
The wiki states that magma's temperature is between 1300-1400°C. Bauxite has a melting point of about 2000°C, so it can survive as a mechanism indefinitely. Iron and Nickel also have high enough melting points, but you can only make mechanisms out of stone!
However, the problem here is not that there are no stones which have high enough melting points. Basically, if you take a look at the matgloss_stone_mineral.txt file in the raws, you can see that very few stones actually have a given melting point. Having done a little research, I can see why. It's hard to get your hands on mineral melting points, as they're not definite things. Different components have different melting points.
After a bit of googling, I managed to find a list of melting points for the mineral Olivine. Almost every source states this mineral has a high melting point. Wikipedia (uuhh) gives a ranges of between 1200-1900°C. The encyclopaedia Britannica website give a range of 1550°C to 1300°C. A few more sources confirm these ranges. Personally, I'm willing to put down a figure of 1450°C for the stone in the game (based largely on the fact that I want to use it for magma safe mechanisms). Since the game needs a single number, I think this is a reasonably fair one to put down in the raw file. However, we should try and discuss this to give the file some veneer of respectability.
====PROPOSAL====
My proposal is this. A group of volunteers take it upon themselves to find as much information about a particular stone in the game as they can, and report back with a list of melting points, etc, and a range of melting point temperatures, and a recommendation. We take a look at the sources, throw around some guesstimates and all come up with what we hope is a reasonably reflective melting point for the stone in the raw file. For completeness, we should even look at stones with given melting points.
When we're finished, we come up with what we hope will be an accurate and complete matgloss_*.txt files for use in mods or even the main game. Hopefully this process will result in some more usable stones for magma projects, and an improvement for the game/mods in general, but we should try to as accurate as possible regardless of the outcome.
A bit of googleing lead me to, at the very least a range of melting points. With a more work and a lot of hands, I think we can come up with similar ranges and sources in good time.
Here are all the stones listed in the matgloss_stone_gem.txt, matgloss_stone_mineral.txt, matgloss_stone_layer.txt and matgloss_stone_soil.txt text files in the raws. This is from 40d11 on linux.
From matgloss_stone_mineral.txt
hematite
limonite
garnierite
native gold
native silver
native copper
malachite
galena
sphalerite
cassiterite
bituminous coal
lignite
native platinum
cinnabar
cobaltite
tetrahedrite
horn silver
gypsum
talc
jet
puddingstone
petrified wood
graphite
brimstone
kimberlite
bismuthinite
realgar
orpiment
stibnite
marcasite
sylvite
cryolite
periclase
ilmenite
rutile
magnetite
chromite
pyrolusite
pitchblende
bauxite
native aluminum
borax
olivine
hornblende
kaolinite
serpentine
orthoclase
microcline
mica
calcite
saltpeter
alabaster
selenite
satinspar
anhydrite
alunite
raw adamantine
From matgloss_stone_layer.txt
sandstone
siltstone
mudstone
shale
claystone
rock salt
limestone
conglomerate
dolomite
flint
chert
chalk
granite
diorite
gabbro
rhyolite
basalt
andesite
felsite
obsidian
quartzite
slate
phyllite
schist
gneiss
marble
From matgloss_stone_soil.txt (Not sure should we bother with these?)
clay
silty clay
sandy clay
clay loam
sandy clay loam
silty clay loam
loam
sandy loam
silt loam
loamy sand
silt
sand
yellow sand
white sand
black sand
red sand
peat
pelagic clay
calcareous ooze
siliceous ooze
From matgloss_stone_gem.txt (This is a long list)
onyx
morion
schorl
lace agate
blue jade
lapis lazuli
prase
prase opal
bloodstone
moss agate
moss opal
variscite
chrysoprase
chrysocolla
sard
carnelian
banded agate
sardonyx
cherry opal
lavender jade
pink jade
tube agate
fire agate
plume agate
brown jasper
picture jasper
smoky quartz
wax opal
wood opal
amber opal
gold opal
citrine
yellow jasper
tigereye
tiger iron
sunstone
resin opal
pyrite
clear tourmaline
gray chalcedony
dendritic agate
shell opal
bone opal
white chalcedony
fortification agate
milk quartz
moonstone
white jade
jasper opal
pineapple opal
onyx opal
milk opal
pipe opal
aventurine
turquoise
rose quartz
rock crystal
black zircon
black pyrope
melanite
indigo tourmaline
blue garnet
tsavorite
green tourmaline
demantoid
green zircon
green jade
heliodor
peridot
red zircon
red tourmaline
red pyrope
almandine
red grossular
pink tourmaline
red beryl
fire opal
rhodolite
purple spinel
alexandrite
tanzanite
morganite
violet spessartine
pink garnet
kunzite
cinnamon grossular
honey yellow beryl
jelly opal
brown zircon
yellow zircon
golden beryl
yellow spessartine
topaz
topazolite
yellow grossular
rubicelle
clear garnet
goshenite
cat's eye
clear zircon
amethyst
aquamarine
red spinel
chrysoberyl
precious fire opal
red flash opal
black opal
white opal
crystal opal
claro opal
levin opal
harlequin opal
pinfire opal
bandfire opal
light yellow diamond
faint yellow diamond
emerald
ruby
sapphire
clear diamond
red diamond
green diamond
blue diamond
yellow diamond
black diamond
star sapphire
star ruby
I'll start by proposig the first entry in our list, with sources
==Olivine===
Source1: (Wikipedia) 1200-1900°C
Source2: (Encyclopedia Britannica) 1300-1550°C
Recommendation: 1450°C
Hopefully we can get at least a few more minerals, and hopefully scrutinise the sources enough to come up with the best recoomendations.