Australian Facetors' Guild Limited

Labradorite

  • 24 Jan 2020 9:19 AM
    Message # 8663840

    From Wikipedia:  Labradorite occurs in mafic igneous rocks and is the feldspar variety most common in basalt and gabbro.

    Sunstone:  The feldspar which usually displays the aventurine appearance is oligoclase, though the effect is sometimes seen in orthoclase: hence two kinds of sunstone are distinguished as "oligoclase sunstone" and "orthoclase sunstone".

    Moonstone:  Moonstone is a sodium potassium aluminium silicate of the feldspar group that displays a pearly and opalescent schiller. An alternative name is hecatolite. Wikipedia.  

    Labdorite appears to be a bastardised name for the "sunstone" from Springsure.   Though the references to this name is numerous in the jewellery world, particularly Kartique jewellery which calls the formerly known as Labradorite from Norway, Finland and Canada as Labdorite.

    How long do we work around this confusion? 


  • 25 Jan 2020 7:02 AM
    Reply # 8672634 on 8663840

    Hi John, 

    The naming issue is why we included a rule in the 2020 Annual Competition Schedule stating all kinds of Feldspar are allowed. 

    Many of us don't have the experience to confidently identify between the felspars.

    Some of the issues arise because of marketing.  For example I have seen  cut Sunstone that looks like Labradorite from Springsure (which I think is Orthoclase) advertised at 6 times the price per carat that I can buy Labadorite for at gemshows.

    So I suppose the answer to your question is ... probably never.  It would take a world wide lapidary body to enforce a uniform naming system and it would end up like the wine industry with regions seeking to have exclusive naming rights for the product of their region.

    I doubt the general population will take to  only calling sapphires and rubies corrundum, and so it is with the Felspar  and Garnet groups.

    Regards

    Gordon


  • 25 Jan 2020 8:44 AM
    Reply # 8673325 on 8663840
    Anonymous member (Administrator)

    The confusion in terminology will continue as long as people freely change names to suit themselves. In the case of the labradorite from Springsure and Hogarth Range, chemical analysis proved that it was, in fact labradorite, even though it looks nothing like the original naming material from Newfoundland. I believe, however, that it is wrong to call it sunstone, when it does not have the inclusions that give the sunstone effect, that we see in the feldspar from Harts Range, for example.

    One thing I have never seen is a good explanation of the reason that the Hogarth Range and Springsure material managed to crystallise in a uniform composition, instead of the alternating layers of changing composition that give the colour effects in the original Newfoundland material.

  • 25 Jan 2020 1:43 PM
    Reply # 8675101 on 8673325
    Anonymous wrote:

    One thing I have never seen is a good explanation of the reason that the Hogarth Range and Springsure material managed to crystallise in a uniform composition, instead of the alternating layers of changing composition that give the colour effects in the original Newfoundland material.

    Well that is a question that I can put to Goldierocks and see what she comes back with.

    Thank you gentlemen.

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