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Kentbrooksite & Nepheline


Kentbrooksite & Nepheline


Description Tabs

Poudrette Quarry, Mont Saint-Hilaire, Québec, Canada
Crystals on Matrix
Size Range: 
Small cabinet (7-10 cm)
4.7 × 8 × 3.5 cm

This is an EDS analyzed specimen of “shocking pink” kentbrooksite. Of course, definitive ID of eudialyte group minerals can only be done via microprobe, but the EDS spectrum is a very good match for what would be expected for kentbrooksite. Please note that color is not a reliable or useful clue for identification of eudialyte group minerals at MSH. 

According to László Horváth (Mindat communication Nov 2010), 80+% of “eudialyte” at MSH is (about equally) eudialyte proper and ferrokentbrooksite. Kentbrooksite is relatively uncommon, making up about 10-15% of the total (with the remainder being manganoeudialyte and oneillite with even smaller amounts of khomyakovite etc.) So this is a somewhat unusual specimen. And it has lots of small, but sharply formed and gemmy crystals. You will need 15-30X to view these crystals clearly.

The first photo (FOV 2.6 x 2.3 mm) shows one of the larger crystals. The brightly lit face spans 0.9 mm.

The second photo (FOV 2.8 x 2.3 mm) shows a slightly larger xl. The brightly lit face spans 1.0 mm. This is probably the largest (single) kentbrooksite crystal on the specimem.

The third photo (FOV 3.6 x 2.0 mm) shows several smaller crystals. The brightly lit one near bottom is 0.8 mm in diameter. There are many similar crystals on the specimen.

The next photo (FOV 4.3 x 2.7 cm) shows the main concentration of kentbrooksite on the specimen. The color is fairly accurate – the kentbrooksite really is “shocking pink”.

There are also several crystal of unaltered nepheline. While nepheline makes up much of the bulk composition of the nepheline syenite at MSH, euhedral crystals are rare.

Some of the nepheline is shown in the center of the next pair of photos (FOV ca 13 mm).

The next photo (FOV 4.4 x 6.3 mm) shows a close-up of these crystals (with more accurate colors). Top to bottom they span 3.9 mm. It is not obvious, but the top edge is damaged.

The back/side of the specimen has more nepheline crystals. Some are shown in the seventh photo (FOV 6.9 x 4.5 mm). The main crystal is 4.8 mm long. It looks somewhat like a “stretched” sodalite crystal, but none of the crystals in this cavity have any UV response either.

Note that USPS foreign packet rates recently increased significantly. By using a small box, I can keep the single item shipping weight just below 8 oz (225 g) for foreign customers. The specimen isn’t particularly delicate so that should work OK and keep the cost of postage from becoming outrageous (which is does above the 8 oz limit). However, any additional items will bump the quoted postage rate by $6 to Canada and by $9 to other destinations.

This is not an issue for USA customers because there is just a nominal increase of $0.20 for each additional ounce. Above a total weight of 13 oz, I will use Priority Mail. Up to 16 oz, the “own box” Priority rate is $8.50 (including packing).

Please see my "Shipping Policy" for details. 

Mineral Data
What's on the rock


Crystal System: 
5.0 - 6.0
Type Locality: 
Kentbrooksite occurrence, Amdrup Firth, Kangerlussuaq Firth, Tunu Province (East Greenland), Greenland


5.5 - 6.0
Type Locality: 
Monte Somma, Somma-Vesuvius Complex, Naples Province, Campania, Italy
Analysis Report - only: Kentbrooksite & Nepheline
LMB minerals

Seller Information

Payment options: offline, paypal_wpp, paypal_wps

Seller's terms and conditions

In addition to the standard terms and conditions, please note the following. Almost all IDs are visual. While in most cases the ID is obvious, there may be cases where it is not. If you are doubtful about a particular ID, please ask for more information. Or do not bid! Similarly, if you are not sure that the specimen meets your criteria, do not bid. I have tdone the best I can with the photos. Nevertheless, if you are not happy with a specimen for any reason, I will refund the bid price – but not the shipping costs (unless the fault is clearly mine) – if the specimen is returned. This policy applies even if analysis of the specimen shows that my ID was incorrect. When in doubt, ask - or don’t bid. Note that most crystals at MSH and Varennes are micros - even if on large specimens. Please pay attention to the stated sizes. Any customs duties, fees etc. are the responsibility of the buyer.