[Rockhounds] opalite vs. not

[Carol Carter-Wientjes]

I bought it from a fellow in Wyoming who is mining it himself but am not 
sure where he's finding it.

Thank you for sending the write up, is very interesting.

----- Original Message ----- 
From: "Kreigh Tomaszewski" <Kreigh at Tomaszewski.net>
To: "Rockhounds at drizzle.com: A mailing list for rock and gem collectors" 
<rockhounds at lists.drizzle.com>
Sent: Sunday, September 23, 2007 8:33 PM
Subject: Re: [Rockhounds] opalite vs. not


> Carol,
>
> I was at Roger Pabian's website at unl.edu looking for something else
> when your email came in, so I also searched for Wyoming (as I remembered
> the location) and found 95 varieties in the Agate Lexicon. The first one
> listed was Opalite; one specimen was reported to be jasperized. Here is
> the full writeup...
>
> Opalite: >From Donald Kasper (personal communication, 2006) Opalite
> is an opalized volcanic tuff or ash that may occur with common opal
> and agate. It may be dendritic. The key distinction between opalite
> and common opal is that opalite is very hard; specimens of opalite
> saw or chip with difficulty, whereas opal is commonly glassy and
> chips easily Opalite may have a wet appearance upon breaking fresh
> specimens creating the illusion of opal. Because of its hardness,
> opalite will commonly be found in pronounced outcrops or ridges in
> localities in the Mojave Desert and other world wide localities,
> while common opal outcrops form muddy, rolling hills or colored soil
> (laterites?). Common opal fractures readily into tiny crumbs upon
> hitting with a rock hammer and opalite does not. Opalite
> probably has a hardness of five to six, and common opal has a
> hardness of probably two. Opalite appears to decompose into sand,
> while common opal appears to decompose into a clay or mud (expansive
> clay). Opalite is associated with deep beds of volcanic ash or
> welded ash flow tuff, so it may occur with deposits of fossil palm
> root, palm wood, and bog in the Mojave Desert region. Opalite is
> often associated with moss agate and plume agate. Opalite can be a
> variety of colors, including white, tan, brown, green, and peach.
> Opal has a brittle fracture to it, while opalite does not exhibit
> this property. It is difficult to test hardness because of
> variability of specimens. Kramer (California) opalite specimens
> appear to be able to scratch Opal Mountain. opal specimens, but just
> barely. A knife can scrath the opal, but not opalite, but I (Kasper)
> do not know if this will be consistent (Knives are supposed to be
> Mohs hardness 5.5). However, the Kramer specimen is jasperized as a
> bog, so it could be harder from that. It's appears that opalite is H
> 6+ and Opal is H 5+. When some say opalite is "massive common opal",
> I (Kasper) think they are refering to its strength achieved through
> combination with tuff and subsequent loss of brittleness. Subsequent
> literature search shows that opalite occurs in the Ogallala
> Formation of Pliocene age in the North American mid-continent with
> extensive deposits being found in South Dakota, Nebraska, Wyoming,
> Kansas, Oklahoma, and Texas. The opalite from Kansas has been
> offered as moss agate for over 100 years, first being reported by
> Kunz (1885) from deposits in Graham County. Opalite also occurs in
> Australia and material from there has been offered as Golden Moss
> Opalite and Blue Moss Opalite in the gem trade. Common dendritic
> opal has been mined from deposits in the Ogallala Formation near
> Angora in Box Butte County, Nebraska. There, the common opal
> occurred in small individual nodules as opposed to thickly bedded or
> ledge forming deposits of opalite.
>
> Where in Wyoming did you find it?
>
> Kreigh
>
>
>
>
> Carol Carter-Wientjes wrote:
>>
>> Thanks Kreigh,
>>
>>  I've seen the opalite glass so know what you're referring to. I don't 
>> know
>> if the terms opalized or common opal would be more proper in place of
>> opalite.
>>
>> I'm pretty good at rock ID's but it sounds like you and many others on 
>> this
>> forum know a lot about compositions of different rock materials right 
>> down
>> to the chemistry. I can tell I'm going to learn a lot from all of you 
>> folks!
>> Thank you so much for your answers and ideas, I've enjoyed taking all of
>> them in. Know it's hard to really determine what something is when all 
>> you
>> have is a photo to go from.
>>
>> And yes Don, this stuff is really neat and the carving I did from another
>> nodule is a GORgeous deep red-grape all polished up. Gotta pic of that 
>> too
>> if anybody wants to see it too.
>>
>> Thank you again, Carol
>>
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