MSH produces perhaps the best crystalised specimens of gobbinsite.

This specimen features several good aggregates of gobbinsite with chabazite-Na (rare at MSH), as well as relatively large areas of powdery dawsonite and a few colorless crystals of sabinaite. There are also small glassy analcime crystals, and very small siderite and albite crystals plus very minor natrolite and polylithionite. In addition, there are several types of pseudomorphs, some of which are REE bearing. Everything sits on a very large, altering, aegirine crystal. The specimen is essentially a very large “micro”, but there is quite a lot to look at under a scope.

The first pair of photos (FOV 3.4 x 5.7 mm) shows a very nice, typically “spiky” aggregate of twinned gobbinsite spanning 1.6 mm, and an aggregate of platy chabazite-Na rosettes spanning 2.1 mm. (The chabazite-Na was verified via PXRD and EDS on another specimen.)

The third photo (FOV 3.1 x 2.3 mm) is an attempt – not too successful – to get a clearer view of the chabazite using higher magnification. This is a 30X view. But the chabazite plates are rounded and sort of “ghostly”. Some of the other chabazite crystals on the specimen are more distinctly hexagonal and transparent. (But others are completely opaque.)

The next pair of photos (FOV 6.3 x 4.0 mm) shows the largest gobbinsite aggregate on the specimen.

There are several other, smaller, gobbinsite aggregates. One of these (ca 2 mm) is shown in the next photo (FOV 3.6 x 2,4 mm) along with small (1.0 mm) sabinaite crystals (on the left) and (0.6 mm) “saucers” of chabzaite-Na (on the right). The chabazite sits on small siderite rhombs. There are a few other colorless sabinaite crystals on the specimen, but sabinaite is just an accessory mineral here.

The seventh photo (FOV 3.3 x 2.0 mm) is a close-up of some more “robust” chabazite crystals ca 0.9 mm in diameter. These crystals have a stacked or layered appearance.

The eighth photo (FOV 6.1 x 4.2 mm) shows some of the pearly, powdery, dawsonite on the specimen. This is far from the largest area of dawsonite on the specimen, but the larger areas have almost no contrast and are not very suitable for micro photography. In this case, the dawsonite coats chabzazite crystals (<= 1 mm). The resulting bumpy texture makes enough contrast for photography.

The ninth photo (FOV 6.8 x 4.3 mm) shows the largest concentration of colorless, glassy, analcime on the specimen. Note that many of the faces “lit up” at the same time, implying that they are parallel or nearly so. I’m no sure if that means that they are somehow all parts of the same, convoluted, crystal, or if the analcime crystals are growing epitactically on something – another analcime crystal?

In the full-view photo, most of the white stuff is albite, but the relatively smooth areas on the right are dawsonite. The red arrow points to the largest gobbinsite arrow. The yellow arrow to the right and below that points to most of the sabinaite (etc.). The yellow arrow on the left points to chabzite-Na and gobbinsite. These minerals are scattered over the top and this side of the specimen. The analcime is mostly at far left center. The brown stuff is siderite. The tan stuff is pseudomorphs. The one at upper right has REE. There are also some (broken) prismatic pseudomorphs, probably after petersenite-(Ce). (Not shown). These pseudomorphs have deep REE absorption lines (mostly Nd). Such stuff was common in the Poudrette pegmatite. These are nothing special.

The back is mostly just albite on aegirine with more siderite.

This specimen is from the core of the Poudrette pegmatite.

This is a heavy beast. Single item shipping weight (no case) is about 11.7 oz. For non-USA destinations, the postage will be painful. The “silver lining” is that the quoted rate is good up to a total weight of 32 oz (950 g). If you have the patience, it may be advantageous to keep an “open box”. Let me know.

For shipments within the USA, I will use “own box” Priority Mail. The quoted rate is good up to a total weight of 16 oz.