Mull Geology (James Westland)
Out past the Lighthouse at Rubha nan Gall again. Dry today. Rocks there are full of some quite large amygdales - mainly quartz and calcite I think. Mentioned in the BGS Memoir. These are low in the sequence lavas - the underlying Jurassic sediments are not far below. Just a little bit further north there are outcrops of Jurassic rocks. Lighthouse approach is made from a red Jurassic sandstone quarried nearby #Mull #geology #basalts #amygdales #calcite #quartz
Nov 13, 2022 at 12:10pmWeb
Show threadAnnabirdianNov 15, 2022
@geologymull ooo nice! Any zeolites?
Show threadMull Geology (James Westland)Nov 15, 2022
@Annabirdian Not so sure about that particular flow. Lots of calcite and quartz in it. But the flows above that one yes zeolites. Seldom big examples though. And there is also Tobermorite! It was along that coast that Heddle first noted it
Show threadAnnabirdianNov 19, 2022
@geologymull I had to Google tobermorite! I'd like to see that!
Show threadJohn Faithfull๐ŸŒ๐Ÿ‡ช๐Ÿ‡บ๐Ÿด๓ ง๓ ข๓ ณ๓ ฃ๓ ด๓ ฟ๐Ÿงก โœŠ๐ŸผโœŠ๐ŸฟNov 19, 2022
@Annabirdian @geologymull Me too! It's abundant in Mull amygdale assemblages if you use XRD, but as it always occurs as fine-grained white masses, it's really hard to know visually whether something like that is tobermorite or not. A devious mineral. ๐Ÿ˜
Show threadAnnabirdianNov 19, 2022
@FaithfullJohn @geologymull to be honest I struggle with all amygdale infills and like to say everything is analcite. I'd like to be better at them...
Show threadMull Geology (James Westland)Nov 20, 2022

@Annabirdian @FaithfullJohn Heddles paper on various minerals, incl Tobermorite is available on line
doi:10.1180/minmag.1880.004.18.04

Some snips from it:-

Show threadAnnabirdianNov 20, 2022
@geologymull @FaithfullJohn ooo nice! Thanks so much!