FMF - Friends of Minerals Forum, discussion and message board

[Greg Toomey]

Excellent specimens everyone! This is a botryoidal fluorite on quartz from Jamner, India. 9.5 cm high x 9.5 cm wide x 7 cm deep. I really like this glandular piece.
Greg

[Gail]

Greg! I have your "egg" twin! I love it too!

[Greg Toomey]

Gail,

I'd love to see it!

Greg

[jamesb]

I like the "egg" fluorite too.

[John S. White]

For some reason these "egg" or "glandular" fluorites were remarkably abundant at this year's show. I probably should have purchased one.

[Pete Modreski]

A few slightly "offbeat" things in exhibits that I enjoyed seeing at the Show...

[vic rzonca]

Got this from Great Wall Minerals, I found the contrasts stunning.

[Matt_Zukowski]

That is interesting looking vic.

[John S. White]

Very nice Vic. For some reason feldspar seem to be underappreciated, except for amazonite.

[keldjarn]

Very nice combination and typical for many miarolitic cavities in granites where the quartz crystals are smoky beacause of the backgorund radiation in the granite.
John, also white feldspar crystals may command high prices. A white microcline from Brazil was posted on the irocks website yesterday and sold at once for USD 6.500.

[John S. White]

That may be a rare exception because in my experience at shows feldspars, very nice ones in fact, tend to me modestly priced and hard to sell.

[vic rzonca]

Could one of you give me a simple explanation of miarolitic?

[keldjarn]

You can find the following definition in Wikipedia:

"Miarolitic cavities (or miarolitic texture) are typically crystal lined irregular cavities or vugs most commonly found in granitic pegmatites, but also found in a variety of igneous rocks. The central portions of pegmatites are often miarolitic as the pegmatite dike crystallizes from the outside walls toward the center. The volatile portion of the magma is gradually excluded from the forming crystal phases until it becomes trapped within the body and forms the cavities which often contain minerals of elements incompatible with the typical silicate granitic mineralogy."

In plain language this means that miarolitic cavities are formed by residual vapor/gas in magmas that may contain a diversity of mineral forming elements. Feldspar has a much higher melting point (ceramics compared to glass) -- and will crystallize first, followed by quartz in the most simple mineral assemblages of such miarolitic cavities in granites.

They are of great interest to mineral collectors not only because well formed and large crystals can form in such cavities, but also because they may host a number of gem minerals and rare minerals in exceptional crystals.

Knut

[Joan Kureczka]

Keldjarn -- Don't believe the prices on that site when a piece sells. And don't believe they all sold immediately either. That was the "list" price, but not necessarily the selling price. And we have seen some pieces go up on that site in a new listing that we knew were sold long before they were posted. Its all marketing.

John is right that most feldspars are relatively modestly priced unless they are blue or have another mineral in association that drives up the price.

[keldjarn]

Joan, of course you and John are right that except for amazonites, yellow gemmy orthoclase from Madagascar and crystallized Mexican moonstone, feldspars are usually cheap - even in good crystals. I only wanted to show that these days when even groups of pyrite crystals are known to have been sold (at auctions) for more than 50.000 USD, it is sometimes surprising what some specimens are sold for. I know also there is a lot fo marketing tricks on the web, but even if this specimen was sold for 20 % of the price mentioned, it would have been a very expensive white microcline !
Knut