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Earth of fire

Actualité volcanique, Articles de fond sur étude de volcan, tectonique, récits et photos de voyage

Located 3000 meters above the sea level , the hill known in his Nahuatl name Itzépetl - itzetl for obsidian, and tepetl for hill - and in Spanish as the Cerro de las Navajas , houses a mine recognized for its obsidian veins of several colors: black , jade green and reddish .

Archaeology refer this place as the main obsidian's supply center of Teotihuacan. Many Toltec and Aztec remains have been found : arrowheads , knives, tomahawks, various decorative utensils and food preparation .

Late Classic obsidian spearheads from the Maya city of Pale   Spearheads in obsidian found at Palenque / Museum of the Americas Madrid - Photo Simon Burchell .

Obsidian was known in pre- Hispanic times as the " stone of the gods " ... what inspired the legend:

A woman named Xochitzol , sun flower , was in love with a warrior. His father, a priest, does not approve the marriage, and sent the warrior to war. Before adjourning , the lovers went on the hill and it sealed a pact of love . Xochitzol said: " I will not marry me before you return."

Time passed and the warrior did not return. Xochitzol climbed the hill again, in order to not stop crying . God asked him the reason for her tears , and how he could console ... Xochitzol implored : " my tears become a shining lighthouse to guide the return of my beloved ." The gods then changed her tears in obsidian .
To date, the love is not returned and she always cries ... her tears became the whisper of the wind , and there is always obsidian for all.

Origin of obsdian's deposits :

A single volcanic region can include a variety of obsidian flows , each characterized by optical and chemical properties clean and different .

Sierra de Pachuca, south of Huasca de Ocampo, has green, gray and brown obsidian.
This rhyolitic volcanic center is located north of TMVB - Trans Mexican Volcanic Belt , and its deposits covering about 250 km², consisting mainly of rhyolitic lava flows and pyroclastic flows, and numerous cinder cones and their lava flows .

Sierra de Pachuca - Parque Nacional El Chico - Eneas De Tro                 
Mexico - Sierra de Pachuca - Photo Eneas de Troya

SierradePachucageologicmap modifiedfromPonomarenko,2004.ElGeological map of Sierra de Pachuca / according Ponomarenko 2004 - the dotted ellipses indicate the important pre -Hispanic mining areas. / In work of Denisse Argote - Espino, references in sources.

Sierra de Pachuca has four eruptive complex , each consisting of one or more lava flows covering the same magma chamber . In all cases , obsidian took place in continuous bands in a broad lava flow .

The first carrier obsidian is the Guajalote flow, southwest , followed by green obsidian Las Minas in flows towards the west and south .
The collapse of the northern flank of the volcano then caused a large debris avalanche and caused explosive eruptions. We can see these deposits , dated to about 2 Ma , near Tulancingo , covering an old pyroclastic flow , which in turn covered observed basalts that gave the
organs of San Miguel Regla. .
The post-avalanche Ixatla flow filled in part the collapse amphitheater,  and is associated with the gray obsidian .
Finally , the complex of rhyolite and obsidian El Horcon covered the collapse scar, overwhelmed and formed the major peaks of the Sierra de Pachuca . The northern and eastern flanks of the Sierra Las Navajas were also covered by the El Horcon flows.

Obsidienne las Navajas - trotamexico
                             Obsidian shards of Las Navajas - Photo Trotademexico

Obsidian from this region presents itself in two forms : either part of the lava flow, either in blocks carted below by an avalanche. The obtaining of obsidian is most often deep mine shafts, and by horizontal multi-branch tunnels penetrating the subsurface layers .

itzépetl - tulancingoculturalarqueologialasnavajas
                               In the mine : veins of obsidian - Photo Tulancingocultural



Sources :

- Obsidian Subsource Identification in the Sierra de Pachuca and Otumba Volcanic Regions, Central Mexico, by ICP-MS andDBSCAN Statistical Analysis/ Denisse Argote-Espino & al. / UNAM - link

- Tulancigocultural -  Los vestigios arqueológicos del Cerro de las Navajas, rica mina de obsidiana - link 

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