THE MINERAL EUDIALYTE

Chemistry: Na₄(Ca, Ce, Fe, Mn)₂ZrSi₆O₁₇(OH, Cl)₂, Sodium Calcium Cerium Iron Manganese Zirconium Silicate Hydroxide Chloride
Class: Silicates
Subclass: Cyclosilicates
Uses: As mineral collection specimens and rarely cut as a gemstone.
Specimens

Eudialyte is a fairly rare cyclosilicate mineral. It is a popular mineral in collections however due to its attractive and distinctive colors. It unfortunately rarely forms good crystals and only occasionally forms any crystal faces at all. Crystals of eudialyte are usually embedded in the host rock, surrounded by other minerals and not showing any hint of a crystal form. The mineral's colors on the other hand are quite pleasant and give the collector an all-together attractive and rare mineral. It can show distinctive colors of a red-violet, pink, blue, yellow and an attractive brown. Much eudialyte on the market today comes from the Kola Peninsula, Russia and can add to one's collection of fine minerals from this wonderful site.

The site at Kola Peninsula is one of several sites around the world that have a strange assortment of igneous minerals and are referred to as Agpaitic Pegmatites. These sites are unusually rich in alkali metals especially sodium. They also tend to be rich in what are sometimes termed "difficult elements", elements that are large and/or have unusual charges. These elements do not fit well into ordinary minerals and are thus excluded from earlier crystallized minerals and must wait for their opportunity to crystallize later. Examples of difficult elements are zirconium, beryllium, strontium, cerium, niobium, thorium, barium, yttrium and other rare earth elements. These normally scarce elements become highly concentrated, relatively speaking, and form some unique and wonderful mineral species. Eudialyte is an example of an unusual mineral that comes from these mineralogically unique sites. Not only is it rich in sodium, but has zirconium, cerium and often traces of yttrium in its structure. Eudialyte is considered to be a potential source of zirconium in the future.

PHYSICAL CHARACTERISTICS:

Color varies from red-violet, pink, blue, yellow and a light brown.
Luster is vitreous.
Transparency: Crystals are translucent to transparent.
Crystal System is trigonal; bar 3 2/m.
Crystal Habit is typically embedded grains and distorted rhombohedral crystals.
Cleavage is poor in one direction (basal).
Fracture is uneven.
Hardness is 5 - 5.5
Specific Gravity is 2.9 (average)
Streak is white.
Other Characteristics: Crystals tend to be fractured and are somewhat brittle.
Associated Minerals include many rare minerals as well as nepheline, feldspars especially albite, and natrolite, quartz, calcite and aegirine.
Notable Occurrences include Mont Saint-Hilaire, Quebec, Canada; Kola Peninsula, Russia; Kangerdluarsuk and Julianehaab, Greenland; the Langesundfjord region of Norway; Madagascar and Magnet Cove, Arkansas, USA.
Best Field Indicators are lack of crystal habit, association with aegirine, locality, color and hardness.