Magnesite, Monteregianite and Mosandrite from
Marcasite in Chalcedony, pair mounted in plaster $35
Bean Field, Nipomo, San Luis Obispo Co., California
These nodules from farmer's fields are locally famous. Chalcedony encloses what look like rosettes of brassy Marcasite : FeS2. The outside of the nodule is indented like an okra pod.
Margarite $55 SOLD
Margarite (CaAl2[(OH)2|Al2Si2O10]) is a member of the Mica group. This large specimen consists of foliated crystals of pearlescent pink-tan Margarite in green Actinolite schist. A reasonably pretty rare mineral, I used to have it on display on my desk shelf. The mines are thought to be the site of either thrust fault slivers of aluminous rock, hydrothermal deposits, or a combination of both. See G. Fred Lincks (1978) “The Chester Emery Mines”, Mineralogical Record, Volume 9, #4 (July-Aug), pages 235-242. I can supply a copy of this Mineralogical Record for $10 when purchased with any of my minerals.
McG9-1 McGuinnessite $32 SOLD
Red Mountain District, Mendocino Co., California (TL)
4.3 cm x 5.3 cm x 3.5 cm
This specimen features McGuinnessite ((Mg,Cu)2[(OH)2|CO3]) in flat-lying radial sprays from the type locality. Like the Bementite specimen further below, this is another mineral named after an American collector/dealer: Al McGuinness (1926-1990).
MR9-1 Miguelromeroite and Ludlockite $125 SOLD
Negra Mine, Pampa Larga district, Tierra Amarilla,
5.2 cm x 3.3 cm x 3.3 cm; largest Miguelromeroites ~ 2-3 mm
Red Miguelromeroite crystals (MnMn2Mn2(AsO3OH)2(AsO4)2·4H2O, top right photo) are scattered on a matrix of tan Arsenosiderite, white Barite, greenish Pharmacosiderite and massive gray Tennantite and Arsenic (bottom right photo). Miguelromeroite is found in only 3 locations in the world. The material from Veta Negra was originally classified as Villyaellenite, and in 2009 was discovered to be in fact Miguelromeroite. One fibrous, golden spray (bottom left photo) of rare Ludlockite (PbFe3+4As3+10O22) completes the ensemble.
Mimetite $72 SOLD
A carpet of glistening cauliflower-shaped Mimetites Pb5[Cl|(AsO4)3] flows up the front, over the top and halfway down the back of this specimen. Smaller bunches coat part of the bottom. The color resembles the spicy German mustard.
MORD5-4 Mordenite $125 SOLD
Jalgaon District, Maharashtra, India
10 cm x 10 cm x 7.5 cm
This very unusually-shaped Mordenite ((Na2,Ca,K2)Al2Si10O24·7H2O) will definitely attract attention to your mineral display. Mordenite is one of the rarer zeolite minerals, and this one has a habit unlike any others that I have ever seen. I can’t even find its like in the mineral archives on www.mindat.org, so it must have been a very limited find.
MORD5-2 Mordenite $275 SOLD
District, Maharashtra, India
This very unusually-shaped Mordenite will definitely attract attention to your mineral display. Mordenite is one of the rarer zeolite minerals, and this one has a habit unlike any others that I have ever seen. The find was very limited.
Murdochite, Brochantite, Linarite
I'll end my first posting to my website with four rarities from Chile. Naked-eye patches of black Murdochite (PbCu6O8-x(Cl,Br)2x, x<=0.5) are visible on the front (left photo) and side (right photo). With magnification (loupe or low-power microscope), square crystal faces are visible. Nice blue accents are provided by elongated Linarite crystals and green spikes of Brochantite. The Malachite ps Azurite appears to be mostly on the bottom, in the form of green tabular replacements.
MUS10-1 Muscovite $28 SOLD
Xanda Mine, Virgem da Lapa, Minas Gerais, Brazil
Here's an oddball Muscovite (KAl2AlSi3O10(OH)2); one side is a classic rosette, while the other side has been etched down the middle, leaving a ridge (bottom & right edges of the right-hand photo - a bit hard to see, sorry). The luster on the etched side is a little dimmer and the color a bit paler.
MIC5-15 Star Muscovite on Feldspar $64 SOLD
Governador Valadares, Minas Gerais, Brazil
9 cm x 7 cm x 3.8 cm
The large Muscovite KAl2[(OH)2|AlSi3O10] star in the middle is unusually wide at 4 cm, and the placement atop the Feldspar is quite attractive. People always ask if the crystal form is natural - it is!
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