This specimen may not look very impressive, but it is. Why? Because, while tephroite is now known from dozens of localities in Japan, and from many others in Austria, Germany, Italy, etc, it is really a rather uncommon mineral. More importantly, crystals of tephroite, even micros are rare. The best ones from the nearby Franklin Mine are only 2-3 mm tall. Larger (but IMHO inferior) crystals were rarely found in the Wessels Mine, and superb, but small, crystals are known from the Eifel pumice and a few other European localities. BUT. This crystal – what is left of it – is 6 x 4 x 4 cm in size!
If you are thinking, “Ah yes. But the crystal is broken”, take a look at the photos in Palache (US Geological Survey Paper 180 – plate 12) or Dunn (Franklin and Sterling Hill, New Jersey: ..., p. 342). If you can find an unbroken crystal of tephroite as large as this, sell the house and buy it.
The first pair of photos shows the front of the specimen in both ambient light and SW UV. The tephroite is the brownish-red crystal at the bottom. As shown in the UV photo, it has the willemite exsolution “network” typical of tephroite from the Sterling Mine. Above the tephroite is a nice mass of deep red zincite and highly fluorescent white calcite. The habit of the tephroite crystal is similar to that shown in Palache (p. 104). The numerous prism faces give cross-sections of such crystals a lenticular appearance. (See the “Analysis” tab. This isn’t an analysis, per se, but the habit and the exsolved willemite clinch the case.)
The second pair of photos shows the “back” of the specimen, where most of the zincite I s visible. In this case, willemite is mostly concentrated along the boundaries between zincite and calcite, but the exsolved “network” in tephroite is visible on the right.
The third pair of photos is the “bottom” of the specimen. It actually consists of somewhat crude faces of the tephroite crystal, covered by a “boundary” crust of (mostly) willemite and unidentified minerals. In this photo, the “front” of the specimen is on the bottom.
The next pair of photos is an attempt to show (what is left of) the tephroite crystal from the “side”. In the photos, the top looks relatively smooth, but it is probably a somewhat weathered fracture. The sides (i.e. prism faces) are more or less fully exposed on the left and partially on the right. These faces aren’t very sharp, and they are encrusted by a mixture of willemite and some unidentified non-fizzy mineral. But for a tephroite crystal of this size, they are really quite noteworthy.
The last pair of photos is an ambient light image of the “front”, rotated about 180 degrees. The color in these photos is too brown, but they may help in visualizing the shape of the tephroite crystal.
The downside to this remarkable specimen is that it is fairly heavy. The single item shipping weight (no case) is about 11.4 oz. That is not a major problem for USA destinations. If the total weight of all items reaches 13 oz, I will use “own box” Priority Mail ($7.75 to $9.50 including packing – varies by destination). That rate is good up to 16 oz.
The quoted rates for other destinations also include packing, etc. and are good up to a total weight of 32 oz (907 g). The specimen itself weighs 8.6 oz (224 g).
