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Mineralogical ClassificationCalcio-Olivine

6th Sep 2005 21:49 UTCChristof

Is Calcio-Olivine, a-Ca2SiO4, a "unnamed mineral" or a variety of olivine?

Christof

6th Sep 2005 23:45 UTCJim Ferraiolo

It is

1. (Calcio-olivine of Bowen)= synonym of monticellite

2. (Calcio-olivine of Oebbecke, 1877)= calcian manganoan forsterite

3. (Calcio-olivine of Shubnikova & Yuferov)= synthetic Ca2

MINERAL database lists 'calcio-olivine' (of Oebbecke, 1877), gamma-Ca2SiO4, with a type locality of Marble Canyon, Culberson Co., Texas, as 'grandfathered'

Strunz & Nickel lists calcio-olivine (of Oebbecke,1877) as a valid mineral name, but as alpha-Ca2SiO4

7th Sep 2005 09:08 UTCMarco E. Ciriotti

Hi Christof and Jim,

in my opinion, calcio-olivine is a valid (grandfathered) mineral , the natural equivalent of the synthetic Ca2(SiO4) of Shubnikova & Yuferov.

It is the Ca-analogue of forsterite/fayalite.

The compound was found in some Eifel localities (i.e.: Bellerberg).

7th Sep 2005 22:18 UTCChristof

Marco and Jim,

it is a bit confusing what is alfa or gamma Ca2SiO4. In cement literature I found alfa-Ca2SiO4 is Bredigite, beta-Ca2SiO4 is Larnite and gamma-Ca2SiO4 is Calcio-Olivine.

Bredigite, Larnite and Calcio-Olivine occur at Bellerberg. For Larnit and Bredigite are listed as valid minerals. But the entry for Calcio-Olivine leads to "Olivine" Var. Calcio-Olivine. Is there something wrong ?

Christof

8th Sep 2005 00:37 UTCJim Ferraiolo

Well, MINERAL database does list calcio-olivine as gamma-Ca2SiO4. I would stick with that.

Strunz & Nickel gives the crystal data for calcio-olivine (alpha-Ca2SiO4) as Orthorhombic, space group Pnma (62), a = 11.22, b = 6.76, c = 5.08A.

MINERAL gives Orthorhombic, space group pnma (62), a = 11.371, b = 6.782 c = 5.091A.

Close enough

I suspect an error crept into one of the databases as to which polymorph calcio-olivine is equivalent to.

8th Sep 2005 07:16 UTCMarco E. Ciriotti

I think that calcio-olivine is gamma-Ca2SiO4.

The Mindat web page for calcio-olivine is now updated.

Ciao. Marco

9th Sep 2005 18:17 UTCMarco E. Ciriotti

If I well remember, the use of the prefixed Greek symbols for the chemical formulae was discouraged by IUPAC.

Someone can confirm?

9th Sep 2005 18:56 UTCJim Ferraiolo

Marco,

I was told by Dr Bayliss that prefixed Greek symbols should not be used in mineralogical formulas because of misuse of the symbols for the wrong polymorph, etc. However I could find nothing in the IMA-CNMMN procedures concerning the use or non-use. IUCr does mention the Greek letter should not be italicized and not be spelled out.

By the way, calcio-olivine in the Mindat listing should be Ca2SiO4, not(Mg,Ca)2SiO4.

9th Sep 2005 20:33 UTCMarco E. Ciriotti

Jim,

you just confirm what I know. Thanks a lot. I agree with Peter Bayliss observations.

Now the Mindat calcio-olivine formula is OK.

Ciao. Marco

19th Mar 2009 17:49 UTCadomin

Christof Wrote:

-------------------------------------------------------

> Is Calcio-Olivine, a-Ca2SiO4, a "unnamed mineral"

> or a variety of olivine?

>

> Christof

http://sportsmovei2.blog.shinobi.jp/

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