Euclase

Euclase Crystal: A beautiful blue crystal of euclase with a nice termination and obvious striations. This specimen measures approximately 2.1 x 1.3 x 0.3 centimeters in size and is from Gachala, Boyaca Department, Colombia. Specimen and photo by Arkenstone / www.iRocks.com.

What Is Euclase?

Euclase is a rare beryllium aluminum hydroxide silicate mineral that crystallizes in the monoclinic system. It has a chemical composition of BeAlSiO₄(OH). Euclase crystals are usually found in granitic pegmatites and low-temperature hydrothermal deposits. Massive to fibrous euclase is usually found in schists and phyllites.

Table of Contents

Rare: Seen by Few Geologists Crystals and Gems for Collectors Physical Properties Geographic Occurrence Rare: Pink-Orange Euclase

Rare: Seen by Few Geologists

It is safe to say that most geologists have never knowingly encountered euclase in the field. It is a rare mineral, they are not expecting to see it, it is usually present in small quantities, and because most euclase is colorless to white it is easily overlooked.

Crystals and Gems for Collectors

Euclase is best known for its prismatic crystals with prominent striations and a beautiful blue color with a light tone. Attractive crystal specimens are prized by mineral collectors. Specimens with excellent blue color and high clarity are often faceted into gems for mineral collectors.

Gem collectors went crazy in 2018 when some padparadscha-like orange-pink euclase was discovered in Brazil. Mineral collectors love the beautiful euhedral crystals of this material, but there wasn't enough to satisfy demand.

Physical Properties

When found in well-developed crystals, euclase can be easy to identify. It often occurs as striated prismatic crystals with chisel-shaped terminations. It also occurs as squat, slightly monoclinic crystals with striations.

Although euclase has a hardness of 7.5, it is a fragile gem. It breaks with perfect cleavage with a pearly luster on the cleavage planes. It is also especially brittle. The name "euclase" is derived from the Greek words eu and klasis, which together mean "good fracture". It is, appropriately, a collector's gem.

Geographic Occurrence

Euclase was first reported from the Orenburg district of Russia's Ural Mountains, where it occurs with other gem materials and gold in stream gravels. The most important source of gem- and specimen-quality euclase today is from Ouro Preto, in the Minas Gerais area of Brazil. Noteworthy euclase occurrences include: Australia, Austria, China, Colombia, Colorado (USA), Germany, Russia, and Zimbabwe.