Would This Be Gypsum ?

[DE&i]

While looking for bivalves such as these Pholodomya I picked up around a quarry last year, i was concentrating on the Blisworth Limestone (Great Oolite) which lies just above the Rutland Formation were I also found some crystals.

 

Here’s a photo I took of the exposed crystals of which I like to collect on a return visit this year.

 

 

Would they be Crystal or could they be Quartz ?

 

 

 

Looking east along the line of the fault plane which forms the exposed face of Lincolnshire Limestone on the right.

 

Figure 1.

 

 

To the left, the downthrown Rutland Formation is capped by Blisworth Limestone, Blisworth Clay and Cornbrash. Where the main fault meets the skyline, the Cornbrash abuts the Blisworth Limestone to form an apparently continuous limestone band, though the fault can be traced from there across the floor of the upper quarry.

 

Figure 2.

 

 

Diagrammatic profile of the Jurassic succession exposed across the graben zone at this site.

 

Figure 2.

 

 

 

 

Regards,

Darren.

[Sacha]

The crystals that are complete look like dolomite crystals that I used to collect from Western NY quarries. Yours appear to be a little more translucent than mine though.

[erose]

They look more like calcite to me. But minerals are not my a strength in any way. But they do remind me of the calcite pockets I see her in Texas. I have seen a variety of forms of Gypsum as well but not like that. I don't see quartz and not sure what you mean by "crystal".

[DE&i]

The crystals that are complete look like dolomite crystals that I used to collect from Western NY quarries. Yours appear to be a little more translucent than mine though.

Hi Sacha,

Thats interesting to no ill have to do a bit more research to see if dolomite can be found from this area.

[DE&i]

They look more like calcite to me. But minerals are not my a strength in any way. But they do remind me of the calcite pockets I see her in Texas. I have seen a variety of forms of Gypsum as well but not like that. I don't see quartz and not sure what you mean by "crystal".

Sorry erose my geological terminology is not the best, I couldn’t decide how to describe them as either a sulphate material or clear crystals in appearance, if that makes any sense.

I’ve just read the most common sulphate mineral is Gypsum.

Found as both massive material, including the alabaster variety; and clear crystals, the selenite variety; and, parallel fibrous, the satin spar variety. Typically colourless to white, transparent crystals, thick tabular to lenticular, sometimes prismatic.

So maby I could rule Quartz out.

[mikeymig]

Its calcite! If I collected this calcite pocket I would hit it with my UV light to see if it fluoresces.

mikey

[DE&i]

Its calcite! If I collected this calcite pocket I would hit it with my UV light to see if it fluoresces.

mikey

Hi mikey,

It could be calcite you say....im not familiar with a UV light is that something i can buy here in the UK and take out into the field.

[JohnJ]

I'm with the calcite camp....

[mikeymig]

You should be able to buy one in the UK. Be careful they have a lot of cheap ones on the market and if you get one don't look into the light (sort wave is dangerous). I have one that you can switch to long or short wave UV. It needs to be dark in order to see the mineral fluoresce or "glow". Most calcite has this property but not all do.

mikey

[DE&i]

Hi mikey,

You should be able to buy one in the UK. Be careful they have a lot of cheap ones on the market and if you get one don't look into the light (sort wave is dangerous). I have one that you can switch to long or short wave UV. It needs to be dark in order to see the mineral fluoresce or "glow". Most calcite has this property but not all do.

mikey

Hi mikey,

Thank you for the info ive found this link...there rather expensive , is that about the going rate , one should expect to pay for it.

http://www.ukge.com/en-gb/UV-Lamps__c-p-0-0-242.aspx

[Ludwigia]

I also agree that we're looking at calcite here, since it appears to have a rhombic form. It's doesn't look like quartz(trigonal) or gypsum (monoclinic),

[DE&i]

Thank you everyone for your input , it seems Calcite is the number contender for this specimen then. On my return visit to this quarry ill gather some samples for some more up to date photos.

Regards,

Darren.

[Chrisalyne]

I agree with everyone, looks like calcite!

I think the easiest way to tell if it's a calcium carbonate is by an acid test (if your able to get your hands on hydrocloric acid 5%) if not, I believe vinegar will work too.

You can also tell if it is limestone or dolamite by this acid test too as Dolomite only fizzes when it's in powder form (when you scratch it into a powder (a nail file will work good) and drop a drop of acid on the powder...limestone fizzes right away without being in powder form...calcite should fizz ALOT when acid is used too.)