Discussions

💬 Home 🔎 Search 📅 Latest

╳Discussions

💬 Home 🔎 Search 📅 Latest

Groups

Recent Images in Discussions

Improving Mindat.orgCitron chrysoprase

26th Jun 2016 17:22 UTCOwen Melfyn Lewis

I was shown a polished stone a couple of days back and told it was 'citron chrysoprase' This worried me because, though the colour was sho' nuff a lemon yellow, the structure did not look like any variety of chalcedony that I have ever seen. So, turn to Mindat....

Mindat give this name as a synonym for nickeloan (i.e. nickel-rich) *magnesite* - and from there it starts to get interesting....

Magnesite (MgCO3) forms a solid solution series with gaspeite (NiCO3) that is occasionally cut as a translucent-opaque gem. It seems to me to follow that 'citron chrysoprase' should be an intermediate in this carbonate series (in which the Ni content is > Ni₅₀ ?).

Accordingly, this would make 'citron chrysoprase' a simple misnomer rather than a synonym for a subvariety of chrysoprase (variety of chalcedony.

Anyone any thoughts on this?

26th Jun 2016 19:33 UTCA. M.

"Real" chrysoprase is - to me - always of green color, not yellow (greek "prasinon" - "green"), it's chalcedony variety.

"Citron chrysoprase" is a name of nickel rich variety of magnesite. It is softer than chalcedony. Definitely different.

26th Jun 2016 21:13 UTCŁukasz Kruszewski Expert

Chrysoprase should be green - it is mainly/totally coloured by Ni-rich silicates (e.g., pimelite, "kerolite", ...). If there are citron-coloured chrysoprases then definitely not from Szklary, Poland - the famous Szklary material is more or less intensely green, somewhat pistacchio green.

27th Jun 2016 00:36 UTCBen Grguric Expert

Citron chrysoprase is purely a marketing term used for pale lime-green coloured magnesite derived from weathering of talc-carbonate altered ultramafic rocks. Nodules of it are found in weathered ultramafics from the Yilgarn Craton in Western Australia, and it is commonly present in the same small scale diggings opened up for true chrysoprase. It is definitely not a variety of chalcedonic silica in the way chrysoprase is, although it is likely some magnesite nodules might have a degree of silica induration in the weathered zone.

Technically it is nickeloan magnesite, and as you mention there is a series extending to gaspeite. In actual fact a lot of WA "gaspeite" is probably closer to the magnesite in the solid solution, than gaspeite.

27th Jun 2016 01:51 UTCOwen Melfyn Lewis

Thanks Ben. That seems to punch its ticket as a misnomer.

Go to top of page