Blue Tiger's Eye

Hardness: 6.5-7 on Mohs scale. Color: Blue to blue-gray with chatoyant bands of golden-brown. Luster: Silky to vitreous. Crystal structure: Fibrous aggregates, typically in parallel formations that cause the chatoyancy. Cleavage: Prismatic. Specific gravity: 3.2-3.3. Exhibits strong chatoyancy, a 'cat's eye' effect, due to fibrous inclusions of crocidolite.

Blue Tiger's Eye is a variety of quartz that forms when crocidolite (a fibrous blue amphibole mineral) fibers are replaced by quartz while retaining the original fibrous structure. This process is called pseudomorphism. Over time, further oxidation can turn the blue 'Hawks Eye' into the more common golden-brown 'Tiger's Eye'. It forms in metamorphic rocks under high pressure and relatively low temperatures. Geological age is typically Precambrian to Cenozoic, depending on the specific deposit.

Predominantly used as a beautiful gemstone for jewelry, including beads (as seen in the image), cabochons, carvings, and ornamental pieces. Its chatoyancy makes it highly sought after. Due to its hardness, it can also be used in certain small decorative items.

Blue Tiger's Eye is also known as 'Hawk's Eye' because of its deep blue color and resemblance to a hawk's eye. It is believed by some to have protective and calming properties, aiding in reducing stress and anxiety. It is closely related to Golden Tiger's Eye and Red Tiger's Eye, with the color variation determined by the degree of oxidation of the iron within the crocidolite fibers. The chatoyancy is what gives it its unique appeal.

In the field, Blue Tiger's Eye is identified by its distinctive blue-gray color and the prominent silky, iridescent luster that creates the 'cat's eye' effect when held under light. The fibrous structure is often visible. It is commonly found in South Africa (Griqualand West), Western Australia, India, and parts of the USA. When identifying, look for the unique banded appearance and the play of light on its surface. Collectors prize well-formed specimens with strong chatoyancy and vibrant color. Be sure to differentiate it from synthetic imitations by checking for natural imperfections and the authentic fibrous appearance.