The Poudrette quarry is the type locality for gaidonnayite. It is uncommon, but not really rare, here. However, most occurrences of gaidonnayite at MSH consists of highly twinned, intergrown, aggregates with inscrutable morphology. Single, or nearly single, are much less common. The two micro specimens in this lot both feature crystals of relatively simple morphology, but different habits and very different responses to SW UV.
The first specimen (1.5 x 1.5 x 1.3 cm) features several simply twinned crystals to ca 1.5 mm. The specimen was found in July 1994 in an “early” part of the Poudrette pegmatite. This specimen is shown in the first 6 photos.
The first two pairs of photos are different views of the largest twin which is ca 1.5 mm (fairly large for the species). (The color balance in the photos didn’t come out quite the same. The first pair is probably more accurate.)
The third pair of photos (FOV 3.6 x 5.5) shows all of the gaidonnayite crystals. Depending on how you count, there are either 4 or 5 twins. The olive crystal in the background is siderite. The bladed white crystals are albite. The largest gaidonnayite twin (shown in the first pair of photos), is at top. The group on the bottom spans ca 2.0 mm altogether.
These crystals fluoresce intense green under SW UV, but are rather pale and can be difficult to pick out under ordinary lighting.
The next four photos are for the second specimen (1.5 x 2.5 x 2.0 cm) which was found in brecciated hornfels in May of 1997and which features non-fluorescent crystals of exceptionally simple shape. The lack of fluorescence is very unusual. There are also a few interesting dolomite crystals.
The first pair of these photos (FOV 2.5 x 2.2 mm) shows nearly colorless crystals. The longest edge on the top crystal is 0.75 mm. The crystals are growing on unusual tabular dolomite (similar to the tabular, hexagonal, rhodochrosite that MSH is well known for). In this photo, reflections used to bring out the morphology, obscure the transparency of the crystals.
The lat pair of photos (FOV 2.3 x 3.2 mm) avoids most of the reflections. The shapes of the crystals may not be as clear, but the transparency may be more obvious. Note that the color is actually a very pale blue or blue-gray. The very thin platy dolomite crystal in the center is 1.3 mm in diameter. The thicker, “rust” stained, platy white crystals are (probably) microcline.
I have not provided full view photos of these specimen because they are micros and, hand held, there is nothing to see.
Combined shipping weight (with one MM case and one TN case) is 3.4 oz (95 g). Outside the USA, the stated postage and packing rate applies up to a total weight of 8 oz (225 g).
Within the USA, there is a nominal increase of $0.20 for each additional ounce. Above 13 oz, I will use Priority Mail. Up to 16 oz, the “own box” Priority rate is $9.25 (including packing).
