Garnet collecting

[expatspain]

About a 50 minute drive from our house is a volcano that last erupted underwater during the Pliocene era. It was part of a fault which stretches from Spain almost to Morocco and emerged from the ancient sea around 6.2 million years ago, moving the shore of the Iberian peninsula 40 KM South. On its slopes are garnets galore which are regularly being washed down from its hollow summit during rains. Sunday we spent an enjoyable couple of hours there, it is open for walking the routes as a public attraction. We regularly spend some time here,  it is called Volcán de la Granatilla or Hoyazo de Níjar. We collected a few hundred garnets

 

[Harry Pristis]

Interesting!  I picked up a few garnets in Erfoud from a fossil dealer, but I had no notion of their origin.

 

[ynot]

Nice haul!

[locktite]

Hi! I live in the same area and am an unrepentant rockhound. I know this volcano well, would  you consider  hanging out with another expat (sort of) so we can share local info ? The area is so abundant in all kinds of great stuff. Thank you!

[Tidgy's Dad]

On 7/27/2022 at 8:51 PM, Harry Pristis said:

Interesting!  I picked up a few garnets in Erfoud from a fossil dealer, but I had no notion of their origin.

 

I think I have a good idea from where these are likely to come.

But before I make an idiot of myself again, are these black, brown or dark red? 

[Harry Pristis]

5 hours ago, Tidgy's Dad said:

I think I have a good idea from where these are likely to come.

But before I make an idiot of myself again, are these black, brown or dark red? 

I believe that those garnets have a reddish cast, Adam, but without a bright light at the margins they appear black.

[Tidgy's Dad]

5 hours ago, Harry Pristis said:

I believe that those garnets have a reddish cast, Adam, but without a bright light at the margins they appear black.

Then they are most likely andradite from Imilchil.

I have a bag of them about somewhere. 

[Oxytropidoceras]

Below are some online publciations about this volcano:

 

El Hoyazo De Níjar: "Arrecifes y Volcanes"

 

Álvarez‐Valero, A.M., Cesare, B. and Kriegsman, L.M., 

2005. Formation of elliptical garnet in a metapelitic

enclave by melt‐assisted dissolution and reprecipitation. 

Journal of Metamorphic Geology, 23(2), pp.65-74.

 

Lunar, R., Martínez-Frías, J., Benito García, R.

and Wolf, D., 1997. Los granates como guía de

exploración y materia prima: El ejemplo del 

Hoyazo de Níjar en el cinturón metalogenético 

del SE Ibérico.

 

Muñoz-Espadas, M.J., Lunar, R. and Martínez-Frías,

J., 2000. The garnet placer deposit from SE Spain:

industrial recovery and geochemical features. Episodes 

Journal of International Geoscience, 23(4), pp.266-269.

 

Martinez-Frias, J., Lunar, R. and Benito, R., 2004.

Th-and U-bearing minerals in the SE Mediterranean

margin of Spain. Episodes Journal of International 

Geoscience, 27(1), pp.33-38.

 

Yours,

 

Paul H.

Edited May 13, 2023 by Oxytropidoceras
added URL and paper

[Harry Pristis]

"The only economic deposit of garnets in Spain is located in the Almería province (SE Spain), forming part of the Neogene Volcanic Complex of El Hoyazo. Due to the high quantity and diversity of the almandine garnets, this area is unique. Garnet occurs as isolated euhedral crystals in the volcanic rock, as the principal component of metapelitic xenoliths in dacite, and as a terrigenous deposit formed by the erosion of the volcanic dome."

 

Now I know more about garnet.  Do my garnets appear to be Moroccan (Imilchil) andradite (mellanite) garnets or do they better resemble the almandine garnets from the NVComplex of Spain?