Ross of Mull Granite at Fionnphort

Fionnphort in the SW of mull at the end of the peninsula called the Ross of mull is a great place to see the well exposed Ross of Mull Granite. The pink granite looks very distinctive , especially in the rays of the setting sun where its pink colour (due to the presence of potassium feldspar) is very striking. There are two locations that are well worth a visit. The first is just south of the ferry slipway, the other is the old quarry at Tormore just north of the village.

 

Fionnphort Slipway Exposures:

 

From the ferry slipway, it is only a short distance to the south where some very interesting intrusions of a dark grey rock cutting the granite can be seen. The rock is noted on the BGS map a "porphyritic microgranodiorite" and is seen to inter-digitate with the contrastingly pink granite. Large crystals of K-feldspar can be seen in the grey material. these are xenocrysts and it is reckoned that the pink granite was not completely solidified when the grey dioritic rock was intruded. Crystals of the pink K-feldspar in the granite were broken of and incorporated in the microgranodiorite.

 

Fionnphort. Looking over to Iona. Ross of Mull Granite on the RHS and forming the large split boulder on the shore

 

Just south of the slipway, intrusions of porphyritic microgranodiorite (grey) cut across the granite (pink)

 

Near this location there is also an obvious fault - the band of dark grey rock has a very obvious displacement across a small steep sided gully. In the bed of the gully can be seen a small dyke - several calcite veins are visible nearby.

 

Tormore Quarry:

 

Tormore Quarry lies to the north of Fionnphort and is accessible by a muddy track from the top of the main car park or else by a rough road which runs past the Ninth Wave Restaurant. Large blocks of granite lie in the quarry and it is a great place to see evidence of how the blocks were cut and transported. The top of the quarry has superb views to the north and west and looks straight over to Iona.

 

View from upper part of quarry down to the pier. Iona in the distance

 

Several dykes of Permian age cut through the granite and one is visible as a large dark feature in the quarry wall. Similar dykes can be found on the shore. These tend to run E-W in contrast to the dykes of the Mull Swarm  which run NW-SE. Aplite veins of much finer grained material are also found. These are best seen just offshore on the island of Eilean nam ban, but you need a boat to get out there. The Staffa tourist boat passes close to this island and the aplite veins are clearly visible from it. The granite generally appears to dip into the Sound of Iona at about 40 degrees. This feature is very noticeable in the Fionnphort slipway. Look north across the bay - it is unmistaleable.

 

There is a small cave "Uamh nam Marbh" (the Cave of the Dead) where bodies were kept before being taken to Iona for burial. it is above the shore just south of the quarry pier.

 

At the shore below the quarry

 

Other photos of the location:

Click on an image to open a larger picture.


Quarried Rock face
Quarried rock face showing where drilled/div>
Interpretative Board

Interpretative board in upper part of quarry
Sinuous Dyke cutting granite

Dyke cutting the granite
Xenolithic dyke

Dyke containing xenoliths
Dyke seen side on in quarry

Dyke seen side on - the large black thing
View to west

Below the quarry at the beach

Beach below the quarry

Beach view
Dyke cutting the granite

Permian dyke cutting granite.

 

Sheets of microgranodiorite cutting the granite  
Sheets of microgranodiorite cutting the granite
 
Close up view of the K-feldspar xenocrysts
Close up view of the K-feldspar xenocrysts



Veining from the microgranodiorite
 
Veining from the microgranodiorite

Eroded surface of the granite  - quartz grains stand proud of the surface
 
Eroded surface of the granite  - quartz grains stand proud of the surface

Joint planes in the granite appear to dip into the Sound of Iona
 
Joint planes in the granite appear to dip into the Sound of Iona

Small gully has a fault running through it
 
Small gully has a fault running through it

Displacement of the sheet caused by the fault
 
Displacement of the sheet caused by the fault

Dyke in the granite, similar to the dykes seen near Tormore quarry
 
Dyke in the granite, similar to the dykes seen near Tormore quarry
   

Similar or related Geological Sites:

Other closely related sites to this one are others that are found within the granite pluton. These include:

 

  • Ardalanish - Contact of the RoMG and the Moine country rocks
  • Knockvologan - Dioritic enclaves in the granite, plus xenoliths of Moine rock
  • Camas - Another quarry and close to the contact with the Moine rocks
  • Iona Erratics - Boulders of RoMG found on Iona, carried by ice
  • Iona East shore: Small islands of in situ RoMG, very close to Iona.

 

Also, and just for interest, the pier at Calgary in the north of Mull is partly made of Ross of Mull Granite.

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