Gypsum/Limestone

[kristian_Fossmo]

Is the addtion of gypsum rock instead of limestone to the subbstrate of limestonegrowing cacti beneficial or does it not do anything? Is it the alkaline properties of limestone the thing that does it for them, or is it the calsium itself?

[cortez753]

It's both, the alkalinity and calcium in limestone that some cacti prefer. Gypsum does not effect ph it's used to add grit to the soil.

[Steve Johnson]

Is the addtion of gypsum rock instead of limestone to the subbstrate of limestonegrowing cacti beneficial or does it not do anything? Is it the alkaline properties of limestone the thing that does it for them, or is it the calsium itself?

Although both contain Calcium, gypsum (CaSO4·2H2O) and limestone (CaCO3) are essentially 2 different minerals. The mineral you select should match what a given calciphyte species is growing in natively. With that said, cacti in cultivation do just fine without it.

[kristian_Fossmo]

I took a trip to a quarry outside my town, but after looking around after information about what I´v found I´m not 100% sure that it is limestone. The swedish word for limestone is , I think, a collective word for both limestone and gypsum. It´s breaks up easely, easely pulverised whit a hammer, white to colour and it makes bubbles in vinegar?

Ok, It´s Astrophytum asterias and Echinocactus horizonthalonius that I´m wondering about? But they maybe do fine without it then?

For the record, my geological knowledge is not wery wide. I´ve never found stones interesting until now.

[Steve Johnson]

Ok, It´s Astrophytum asterias and Echinocactus horizonthalonius that I´m wondering about? But they maybe do fine without it then?

Going on 3 years since I got it, my A. asterias is doing great with a fairly coarse pumice-decomposed granite mix and nothing else.

[adetheproducer]

My a.asterias and a . myriostigma both in granite/limestone/sandstone mix all doing great. Not so sure my a.capricorne likes it though.

[iann]

Gypsum will bubble in a strong enough acid (nasty gases, don't inhale), but household vinegar shouldn't do anything. Limestone and related calcium carbonate minerals bubble in dilute acids, sometimes quite slowly, and produce carbon dioxide which is relatively benign. Some limestones are harder than others. Certainly nothing short of a hammer should fracture it. My local limestone needs quite a big hammer!

[kristian_Fossmo]

Ok, thank you all wery much for helping me out here. I´m going for that it is indeed limestone I´ve collected. Here´s a picture of the mineral itself if that helps to ID it.

DSC_2771.jpg (55.05 KiB) Viewed 2618 times

For experimental purposes I´m going to ad the mineral in one of the pots to see if I can spot any differenses in time. Since I´m growining from seed that will probebly take a while.

Pumise and lavarock is on the way as we speak, granit is spread all over the walkways in wintertime here, so I´ve got litterly tons of it right outside my doorstep in perfecly sized bits and various color!

[kristian_Fossmo]

By the way, adetheproducer, I see you have an excellent taste of music

[adetheproducer]

Those stones look like gypsum, similar to the alabaster we have locally in south Wales. Hard crystals that do not dissolve should be right.

Also cheers kristian_Fossmo.

I also use dolomite in my mixes which is pretty easy to come most of my Mexican species have this included with great results in particular the lophophora love it.

[kristian_Fossmo]

Now I´ve been in contact whit the geological institute here in Sweden, it seems like we dont have any big collections of gypsym here in sweden, just scattered small quanteties in cracks and cavates in some locations. He belived that it was indeed limestone, possibly dolomite. So i´t narrowed it down a littlebit.

[adetheproducer]

Any of those three would be good for calcicole cacti. The limestone deposits in our area are primarily limestone with dolomites inclusions as well as various mineral impurities including gypsum and other metals like iron and aluminium so could be a a good add ingredient to your mixes it works with my plants. It does not look to be all that absorbent a mineral you have there so may wish to include some kind of volcanic lava/pumice/sandstone or some other air and water retaining aggregate if you are using a pure mineral mix.

P.S.
While I think of it a quick and useful test would be to hit it with a hammer, when I crush my rocks to make my soil mixes I do it by hand with a heavy hammer, the dolomites and alabaster give a very clear sulphur smell almost like rotten eggs but not quite as strong. The pure limestone has little odour at all.

[kristian_Fossmo]

No smell to it when hit with a hammer. Pumice is on the way. I´m thinking of including a small amount of organic loam based soil with a little homemade compost mixed in to most of the species (south american), but the ones regarding this topic I´m thinking pure mineral.

[adetheproducer]

Sounds like it is limestone then. Should be good with your Mexicans be careful with loam and compost it will harbour fungi, bacteria and water which can be bad news in our cooler climates. Im in the process of going pure mineral with all my cacti much better results with my mexican species. All my eriosyce now in pure mineral now but still will keep most of my gymnos in actual dirt they seem to like it.

[kristian_Fossmo]

It´s a wery sandy loam soil. Breaks up nice and easy when wet and compressed in the hand, stays realy sandy when dry. Thinking in the terms of 10% organic with the south american species to begin with.