Oltu stone aka black amber

Amber

Amber is fossilized tree resin , which has been appreciated for its color and natural beauty since Neolithic times. Amber is used as an ingredient in perfumes, as a healing agent in folk medicine, and as jewelry. There are five classes of amber, defined on the basis of their chemical constituents...

, is a kind of jet

Jet (lignite)

Jet is a geological material and is considered to be a minor gemstone. Jet is not considered a true mineral, but rather a mineraloid as it has an organic origin, being derived from decaying wood under extreme pressure....

 found in the region around Oltu

Oltu

Oltu is a town and district of Erzurum Province in the Eastern Anatolia region of Turkey. The mayor is İbrahim Ziyrek . The population is 19,969 .-History:...

 town within Erzurum Province

Erzurum Province

Erzurum Province is a Province of Turkey, in the Eastern Anatolia Region of the country. It is bordered by the provinces of Kars and Ağrı to the east, Muş and Bingöl to the south, Erzincan and Bayburt to the west, Rize and Artvin to the north and Ardahan to the northeast. The provincial capital is...

, eastern Turkey

Turkey

Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...

. The organic substance is used as semi-precious gemstone

Gemstone

A gemstone or gem is a piece of mineral, which, in cut and polished form, is used to make jewelry or other adornments...

 in manufacturing jewellery.

Location and extraction

Oltu stone, sometimes called also "Erzurum stone", is principally mined in the villages northeast of Oltu town, around Tutlu Dağı (Yasak Dağ) as well as in Alatarla, Hankaskışla and Çataksu villages. The mountainous, rough region with steep slopes is 1600–1800 m (5,249.3–5,905.5 ft) high.

Oltu stone beds are formed when fossilized trees are subject to diastrophism

Diastrophism

Diastrophism refers to deformation of the Earth's crust, and more especially to folding and faulting. Diastrophism can be considered part of geotectonics. Diastrophism comes from the Greek word meaning a twisting....

 resulting in folding. Beds of this organic substance are 70 centimetre in thickness. Extraction is done by digging narrow tunnels and shafts below ground. There are around 600 quarries in the region.

Properties

It is a very dense mineral-like substance

Mineraloid

A mineraloid is a mineral-like substance that does not demonstrate crystallinity. Mineraloids possess chemical compositions that vary beyond the generally accepted ranges for specific minerals. For example, obsidian is an amorphous glass and not a crystal. Jet is derived from decaying wood under...

 of the nature of coal that does not demonstrate crystallinity. It generally comes in black, but can also be velvet-black, blackish brown, grey or greenish.

Oltu stone's most interesting characteristic is its softness when excavated. It only begins to harden when exposed to the air. For this reason, it can be carved very easily.

It attracts, by way of static electricity

Static electricity

Static electricity refers to the build-up of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge. Static electricity can be contrasted with current electricity, which can be delivered...

, light substances like dust when rubbed. Oltu stone burns bursting in flames, and leaves ash behind.

To distinguish true Oltu stone from the artificial jet, it is rubbed against unglazed porcelain. Real Oltu stone will leave a chocolate brown streak. The structure of Oltu stone, which is remarkably like the wood, can be seen under magnification.

Jewellery

Oltu stone is cut or carved in desired form and polished to manufacture various decorative ornaments and utensils like ring

Ring

Ring may refer to:*Ring , a decorative ornament worn on fingers, toes, or around the arm or neck-Computing:* Ring , a layer of protection in computer systems...

s, earring

Earring

Common locations for piercings, other than the earlobe, include the rook, tragus, and across the helix . The simple term "ear piercing" usually refers to an earlobe piercing, whereas piercings in the upper part of the external ear are often referred to as "cartilage piercings"...

s, necklace

Necklace

A necklace is an article of jewellery which is worn around the neck. Necklaces are frequently formed from a metal jewellery chain. Others are woven or manufactured from cloth using string or twine....

s, bracelet

Bracelet

A bracelet is an article of jewelry which is worn around the wrist. Bracelets can be manufactured from metal, leather, cloth, plastic or other materials and sometimes contain jewels, rocks, wood, and/or shells...

s, tie pin

Tie pin

A Tie pin , is a neckwear-controlling device, originally worn by wealthy English gentlemen to secure the folds of their cravats, they were first popularized at the beginning of the 19th century...

s, smoking pipe

Smoking pipe

A smoking pipe for tobacco smoking typically consists of a chamber for the combustion of tobacco and a thin stem ending in a mouthpiece...

s, cigarette holder

Cigarette holder

A cigarette holder is a fashion accessory, a slender tube in which a cigarette is held for smoking. Most frequently made of silver, jade or bakelite , cigarette holders were considered an essential part of ladies' fashion from the mid-1910s through the early-1970s, and are still widely popular...

s, and prayer beads

Prayer beads

Prayer beads are used by members of various religious traditions such as Roman Catholicism, Orthodox Christianity, Anglicanism, Islam, Hinduism, Buddhism, Sikhism and Bahá'í Faith to count the repetitions of prayers, chants or devotions, such as the rosary of Virgin Mary in Christianity and dhikr ...

.