Sunday, December 13, 2015

Agate lapidary slabs

We mentioned several posts back that we had coming in items from an old Rock Collection. 

Today, we were able to unpack a box that was full of mostly agate polished slabs.  

(Posted below is the Wiki-pedia definition of agate. PS, please check out Wikipedia and make sure to donate to keep them up and running free of charge!) 

Here in the Museum, we are learning about all these rocks as they come in. We are reporting here from a layman's perspective, not as geologists or even rock collectors, so hope you pros out there can bear with us and offer your more educated comments on what you see... PLEASE! 

Now, back to the box....

As you can see, there is a huge variety of colors, formations and sizes, shapes  ... 

This pretty piece is a nice thin slab with crystal formations there in the right hand side. Colors are purple, orange, yellow and white banding. We held it up to the window and it would make a very pretty hanging window piece.

This piece is actually a slice of "Thunder egg", at least that is what "google says".  Those white bands are not flash marks, they are truly opaque white banding in the upper portion with the lower portion being white banding around some crystallization.  Very pretty.

This photo didn't come out very well... doesn't show the colors true, but you can get the idea of the banding and the crystals in the center. Nice piece.

This piece below is one of my favorites. I have been told it is petrified wood. Love the brecciated portions. 
(Breccia (/ˈbrɛiə/ or /ˈbrɛʃiə/) is a rock composed of broken fragments of minerals or rock cementedtogether by a fine-grained matrix[1] that can be similar to or different from the composition of the fragments.)  See, always learning!

All of these pieces have been processed and are now available for purchase. Prices range from $5 - $70+


From Wikipedia, the free encyclopedia
Agate banded 750pix.jpg
Banded agate (agate-like onyx); the specimen is 2.5 cm (0.98 in) wide
CategoryQuartz variety
(repeating unit)
SiO2 silicon dioxide
ColorWhite to grey, light blue, orange to red, black. banded
Crystal habitCryptocrystalline silica
Crystal systemRhombohedral Microcrystalline
FractureConchoidal with very sharp edges.
Mohs scalehardness6.5–7
Specific gravity2.58–2.64
Refractive index1.530–1.540
Birefringenceup to +0.004 (B-G)
Agate /ˈæɡət/ is a cryptocrystalline variety of silica, chiefly chalcedony, characterised by its fineness of grain and brightness of color. Although agates may be found in various kinds of rock, they are classically associated with volcanic rocks and can be common in certain metamorphic rocks.

No comments: