Rémondite-(Ce) is a very rare mineral, known only from a half-dozen localities. MSH is not the TL, but judging by the number of posted photos, MSH is the best pace to find it. However, it is quite rare here.
There are several habits for rémondite-(Ce) at MSH, the most common being the radiating “witch’s brooms” of long prismatic reddish-orange or acicular silvery-gray crystals. This specimen features crystals of the more robust third habit. Unfortunately, the crystals are embedded in a mass of tiny “dogtooth” calcite crystals. There are several well-developed prism faces but no terminations. However, even partial crystals of this type are rare.
A sample of rémondite from this specimen was analyzed via qualitative EDS (see scan #272 under the “Analysis” tab). Chemically, rémondite-(Ce) and petersenite-(Ce) are very similar. Qualiative EDS by itself is probably not sufficient to distinguish these minerals. However, most habits of rémondite-(Ce) at MSH, including this one, are visually distinct from petersenite-(Ce).
Visually and chemically, rémondite-(Ce) coul also be confused with calcioburbankite, but the latter has essential Ca and shows a more substantial Ca peak in an EDS scan (as well as more Sr). The actual ammount of Ca in the type material for these species is not all that different. The chief diference is actually more Na in rémondite-(Ce), which is not easily detected with the equipment used. However, scan #272 is virtuallly identical with that for another type of rémondite-(Ce) that would not be mistaken for calciburbankite. For comparison, I have included scan #273 - and a mini-photo - for this type.
Under tungsten or LED lighting, the rémondite appears to have an orange-salmon color, but under CFL it looks pale chartreuse – the almost the same color as the surrounding calcite – and becomes nearly invisible when hand-held. The rémondite exhibits extremely strong REE absorption lines with a gemological spectroscope.
In addition to the rémondite and calcite, the specimen has franconite, powdery snow-white dawsonite, blue sodalite, clear analcime, and small, but sharp, crystals of aegirine. All are small and none of them is significant. I list them so that you will know what is there.
The first pair of photos (FOV 3.2 x 2.0 mm), shows the best rémondite on the specimen. The largest crystal is only 1.4 x 0.7 mm, but both crystals are terminated and exhibit the stubby, short-prismatic, habit of this type of rémondite-(Ce). There are also a few small, well-terminated aegirine crystals.
The second pair of photos (FOV 4.4 x 6.3 mm) shows two relatively pale, nearly complete prisms of rémondite-(Ce). These larger, more elongated, crystals grew wall-to-wall in a small cavity and have no terminations. Also in the cavity is a broken siderite crystal and aegirine.
Single item shipping weight (no case) is 2.9 oz (82 g). For shipments outside the USA, up to a total weight < 8 oz (225g), this can be combined with items from this or other auctions for the same postage.
Within the USA, postage increases by about $0.20 per ounce. Above 13 oz, I will use Priority Mail (ca $9.25 including packing – varies by destination).
