Joined: Sun Oct 04, 2009 11:18 am Posts: 595 Location: Madrid, Spain
Thomasset, you are the absolute winner of this contest, CONGRATULATIONS!
Here is your
The names of all three minerals come from different forms of "deceiver" because they were frequently confused with other minerals: apatite with beryl, phenakite with quartz and sphalerite with galena!
BTW, the same name is very appropriate for phenakite also because of it's behaviour on diamond tester!
I am honest: I find phenakite with google images I find the answer comparing the stones with classic gems http://www.gemstonediscovery.com/ But I am glad.
Joined: Sun Oct 04, 2009 11:18 am Posts: 595 Location: Madrid, Spain
Alberto wrote:
Conchoidal fracture???
Alberto, I've broken many kilos of sphalerites for cutting and I've never seen conchoidal fracture on it... It's just impossible for mineral with perfect cleavage in six directions!...
Joined: Fri Oct 19, 2007 5:04 pm Posts: 1642 Location: Walnut Creek, CA
Egor Gavrilenko wrote:
Alberto, I've broken many kilos of sphalerites for cutting and I've never seen conchoidal fracture on it... It's just impossible for mineral with perfect cleavage in six directions!...
I agree: I've hammered many small pieces of sphalerite (not for gemological purposes...) to get as perfect cleavage planes as I could, and it was very easy. (on a second thought, I should have kept some pieces for faceting, but it was long before I started faceting: it was the light yellow one from Picos de Europa) And also the black-ish sphalerite I mined from the mines here in Northern Italy once hammered shows nice cleavage planes. Not conchoidal at all.
Joined: Sun Oct 04, 2009 11:18 am Posts: 595 Location: Madrid, Spain
Wow, it looks like we have one more gem for "deceivers" family - malaya garnet !!!
Quote:
Malaya [Pyrospessartite]
The name of this variety of the pyrope-spessartite series is not related in any way to the area of southeast Asia known as Malaya or its people. It is derived from the word of the Swahili tribe in Africa meaning prostitute. Joel Arem in the Color Encyclopedia of Gemstones attributes it to the Bantu tribe word for “outside the family” or “deceiver”. According to unconfirmed reports, miners, frustrated in their search for a different mineral and disgusted by the frequent presence of such a similar material, bestowed the unflattering name on the similar substance. The sources in Africa provided the name, but, perhaps, the use of the term pyrospessartite combined with the designation of the place of origin, Tanzania, would create less confusion.
good to know Egor, thx........someone should drop a note to Dr Bill........GTPro reports Sphalreites fracture as "conchoidal to uneven"..........
OK, I don't get out much (it only took me 7 months to find this). I name my source for the misinformation in GT Pro about Sphalerite fracture as GIA's Gem Reference Guide (copyright 1988 - maybe that's why). I'll fix this in the next release.
_________________ Information is King. Bill Wise Gemology Tools Professional http://www.gemologytools.com (if you use a Windows machine) http://www.gemologytoolsonline.com (if you use a Mac or iPad)
No problem, Alberto. It's not your responsibility to keep me up to date.
_________________ Information is King. Bill Wise Gemology Tools Professional http://www.gemologytools.com (if you use a Windows machine) http://www.gemologytoolsonline.com (if you use a Mac or iPad)
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