[Rockhounds] when volcanoes drop bombs: giant crystal payload

[Lanny]

I've stopped at Cinder Butte three times. The first time was around 15  
years ago there was a lot of the feldspars lying around. Most were 
pieces, a few were complete or nearly complete crystals. The few good 
crystals all had a red coating, looks like an iron oxide/hydroxide on 
most, looks like the lava on others. Most were broken pieces, all had 
many fractures/cleavages showing, exactly like those in Don's photos. 
If one is into faceting, it was no problem finding pieces with good gem 
quality areas that could cut small stones of pale yellowish color.

The second time, more work had been done. The large pit on the north 
side of the butte had been enlarged and an area on the west side of it 
had a lot of cinders removed cutting a rump up the cone. I saw very 
little that time.

The third time, it was really hot, I was not in a good mood having been 
out in the heat (upper 90s to 102 for three days already and I hate 
that kind of heat). I drank somewhere between 1 quart and a thousand 
gallons of water while there in the evening for only an hour and saw a 
lot of the feldspars. Again, mostly pieces, some large, up to about 1 
1/2 inches, but, as memory recalls suggests (and it isn't dependable) 
found only one fairly decent complete crystal. I kept the few broken 
pieces with the larger gemmy areas.

The only suggestion I have for finding the feldspars is walk around the 
disturbed areas looking carefully. Generally the broken pieces are easy 
to spot because of the light transparent appearance against the black 
and red cinders. The complete crystals are more difficult because with 
the coating they are the same color and nearly the same texture; it's 
more of a lucky break to look right at one and spot it because of the 
shape. The angle of the sun can make a difference too.

So, from my experience, it is a hit and miss thing depending perhaps on 
just what zone/layer of the cinders has recently been stirred up by the 
county, the angle of the sun and how well the collector's eyes are 
working that day. Good luck when you try it again. I keep thinking of 
going back, it's been 12 years since the last time, but I don't seem to 
be getting over in that part of Idaho when not on a long drive to or 
from somewhere else.

Regards,

Lanny




On Aug 1, 2007, at 4:31 PM, John Junkroski wrote:

> This sounds very much like a site we visited a few weeks ago after 
> digging at the Spencer opal mines.
>
> A local gentlemen suggested that we drive out and assured us that 
> access was no problem since the local road commission was using the 
> cinder cone as a source for road-fill.
>
> We spent the better part of an hour exploring three or four recently 
> active pits and found nothing other than a few 1/4 inch  yellowish,
> opaque crystals that I could not identify. I picked up an awful lot of 
> (boring) black basalt and found nothing worth bringing home.
>
> If anyone has any suggestions on how to locate the "sunstone"on the 
> cindercone I would greatly appreciate hearing them, as we intend to go 
> back to Spencer early next Summer.
>
> Opal is great fun, and the people at the Spencer mine are wonderful 
> hosts.
>
> John
>
> On Aug 1, 2007, at 10:54 AM, Tim Fisher wrote:
>
>> Whoops, my bad I was thinking of another site. Anyway its Cinder 
>> Butte, SE of Spencer, and it's in Lanny's book. If it's sunstone it's 
>> automatically plagioclase, at least until some was analyzed and found 
>> to me andesine lol.
>>
>> At 08:30 AM 8/1/2007, you wrote:
>>
>>> Pmodreski at aol.com wrote:
>>>
>>>
>>>>
>>>> In a message dated 8/1/2007 8:06:12 AM Mountain Daylight Time,
>>>> nospam at orerockon.com writes:
>>>> It's  sunstone, it is from a well know collecting site on a cinder 
>>>> cone in WY  just over the ID border.
>>>> Ah, but sunstone is a descriptive term, is it sanidine or 
>>>> orthoclase?
>>>> Probably orthoclase.  Don, the master feldsparologist, will 
>>>> certainly find  out.
>>>>
>>>
>>>
>>> Holy cow, what a way to start the morning.  OK, in sum, I can say 
>>> the gentleman definitely found it in Idaho; so perhaps there is more 
>>> than one volcanic field with this type of formation?  I never had 
>>> volcanology so I don't know if this could have blown that far from 
>>> WY.
>>>
>>> The geologist who is working with these kept calling them 
>>> plagioclase. But there is no point in speculation or pontification 
>>> until we get a chance to look at them.  He had some of them prepped 
>>> for mass spectrometry so I suppose he'll know the trace elements and 
>>> REEs soon.
>>> I will try to x-ray them today but maybe someone else is using the 
>>> instrument.
>>>
>>>
>>> Don
>>>
>>
>> Tim Fisher
>> Ore-ROCK-On!
>> Email address at http://OreRockOn.com
>> -- 
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