Quartz (Var: Chalcedony) : SiO2, Chert

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Copyright © Norman King
minID: KCC-9NX

Quartz (Var: Chalcedony) : SiO2, Chert

Copyright © Norman King  - This image is copyrighted. Unauthorized reproduction prohibited.
Dimensions: 11.6 cm x 8.8 cm x 6.0 cm

This thunderegg-like rock is from near the extreme southern limit of the Columbia Plateau Lava Province in northeastern California. It is largely purple-gray to red-brown, nearly opaque chalcedony topped by large, brown-surfaced botryoids, containing scattered cavities lined by white mini-botryoidal chalcedony with chert, and tiny crystals of an unknown mineral that line the inner surfaces of those cavities (red arrow shows one such cavity). This specimen was given to me in 1959 by an older couple who had it in their rock garden in Adin, Modoc County, California (where that couple and I lived at the time). They were not very knowledgeable about minerals and did not remember precisely where it was found, but said they had not traveled far, so I guessed its origin is Modoc County. It also resembles features seen in some Oregon thundereggs, however. The three daughter photos show details of the thunderegg’s history gleaned from thin sections that I cut (last week) nearly 60 years after I acquired it. It’s amazing what I missed all those years! Collection, thin sections, and photographs by Norman King.

This photo has been shown 100 times
Photo added:27th Aug 2018
Dimensions:2000x1572px (3.14 megapixels)
Date/Time of Photo:17th Aug 2018 18:13:14
Camera:CANON PowerShot SX10 IS
Software:Adobe Photoshop Elements 2.0
Exposure time:1/60s
Focal Length:5mm
ISO speed:100

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