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Ummm ... The different references have contradictory chemical formulas. I trust the one from Mindat.org. (Na, Ca)8 (Al6 Si6 O24) (S, SO4, Cl2). Please, a geologist sort this out.— Preceding
unsigned comment added by
65.33.212.34 (
talk •
contribs) 09:34, 4 March 2011
One of the important things is that is contains the
S3- ion to give it colour. That is not apparent in the formula, all we have is "s".— Preceding
unsigned comment added by
Graeme Bartlett (
talk •
contribs) 12:02, 4 March 2011
Can you cite an authoritative reference for that formula?
The formula in the article essentially follows the Hurbut and Klein reference, (the ref I used back in Jan. 06) the Handbook of Mineralogy ref only varies by adding hydroxide. Both of those are "authoritative refs". The Webmineral data site provides a shorter version and the Mindat website seems to be offline right now.
Vsmith (
talk)
13:58, 4 March 2011 (UTC)reply
Mindat accessed now and they agree with formula given - the diffs are mainly sleight variations in order and paren locations.
Vsmith (
talk)
14:11, 4 March 2011 (UTC)reply
There is a purist approach that one chemical formula and one crystal cell is one mineral, but reality is less strict. There are liquid IMA/CNMNC valid minerals (
mercury), amorphous IMA/CNMNC valid minerals (
allophane), and mineraloid IMA/CNMNC valid names (
opal). Many minerals have a chemical formula as a range, some minerals don't have a complete description, yet.
Lapis lazuli is the most expensive blue color of the antiquity, and Lazurite's
chemical formula is one that is given as a range Na6Ca2Al6Si6O24[(SO4), S, Cl, (OH)]2. --
Chris.urs-o (
talk)
12:59, 5 March 2011 (UTC)reply
Sorry, but you mix things up:
Reality is:
each mineral has an IDEAL formula, that is COMPLETELY INVARIABLE; if an ideal formula is variable then we have more than a single mineral
"one crystal cell is one mineral": this doesn't make sense at all
a crystal cell is a UNIT cell of a crystal; one crystal is a mineral, another one (e.g., a crystal of a virus; or any synthetic compound) is not - as simple as it is
mercury IS NOT A MINERAL........... it is a mineralloid; also, mercury ALWAYS has the formula "Hg"
allophane is not a mineral --- is is amorphous; however, it was known prior to IMA --> now it has the "grandfathered" status; it will soon be discredited
Lapis lazuli IS NOT A MINERAL - it is actually a rock...
This is, obviously, complex, because mineralogy has its own rights, as explained/set by the IMA (i.a.).
1.There are various types of formulas. Chemistry has its own types, and mineralogy has its own.
2. Each IMA-approved mineral species has an ideal formula (that may be, but does not necessarily has to be, a structural formula), and this formula is invariable.
3. Some people think that the parentheses with diadochy systems in minerals' formulas are mandatory. The reality is: sometimes yes (e.g., cation order case; stabilization of otherwise metastable structures), but usually not.
3. A lot of mineral species were first analyzed using old techniques; new techniques (e.g., micro-tts-diffraction, Pseudo-Gandolfi diffraction, neutron diffraction, PIXE/PIGE, micro-XANES, etc.) may sometimes show these species to:
(a) have a different structure (i.e., a better structural model is obtained) --> new formula
(b) turn out to be a mixture of more than a single species
Lazurite is not what was thought to be some years ago. New Russian data clearly shows it to be very rare, currently exclusively known from the Malo-Bystrinskoe deposit (Russia). ALL the lapis lazuli material is LACKING LAZURITE. The blue colourant of the Afghan rock is haüyne. Also, the correct formula is: Na7Ca(Al6Si6O24)(SO4)(S3)·H2O.
Eudialytos (
talk)
07:53, 27 June 2023 (UTC)
Refs.:reply