[Rockhounds] re Allende meteorite

[Pmodreski at aol.com]

In a message dated 7/1/2008 5:34:47 PM Mountain Daylight Time,  
SMKELL45 at aol.com writes:

got hold  of a sample of the Allende meteorite, CV-3. I recognized  the  
chondrules and the calcium-aluminum inclusions. Does anyone know if  the  
CAI's are 
a recognized mineral? I like my labels to be as  descriptive  as possible. 
Thanks smkell  





Now there's a question I can't resist trying to help answer--not something  
I'd ever thought about before, specifically.
 
Doing a little web browsing, I'm seeing,
 
"They [CAI's] consist of high-temperature minerals, including silicates and  
oxides of calcium, aluminum, and titanium."

"Refractory inclusions or CAI's (Calcium Aluminum-rich Inclusions) are a  
mineralogically and chemically diverse group of structures mainly seen in  
carbonaceous chondrites. 
"Fluffy Type A's are perhaps the most altered of CAI's. ... The  primary 
mineral assemblage of these inclusions is melilite, V-rich spinel,  perovskite, 
and hibonite."
 
"We have made a detailed examination of the mineralogy, textures, and  
assemblages of six calcium-aluminum-rich inclusions (CAI) in the Allende  meteorite. 
They can be classified into four types - hibonite-bearing, fassaite-  and 
olivine-bearing, feldspathoid-bearing and fassaite-bearing CAI that are  hibonite 
and olivine free. ..."
 
It sounds like the CAI's are composed of a wide variety of minerals; so,  
trying to label one as to its mineral composition, is sort of like taking a  
sample of basalt, and labelling it as to what minerals it's composed of--except,  
I think there are a lot more minerals in the CAI's than in typical basalt.
 
Cheers,
Pete




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