Builder's sand is more coarse and is preferred.

Thank you. I appreciate your response. :)

Unless your soil already contains some organic material (compost, bark fines, etc.), you will probably want to add some, along with the coarse sand.
Red clay+sand+moisture+sun=Adobe Brick!
Rb

LOL! That would be awful. :) Yes, I'm going to have to add some mushroom compost or something because red clay "brick" describes exactly what's up there right now. :D

I think if you mix fine sand in with clay you get concrete, so that's why you're supposed to use the coarser sharp sand or builder's sand.

I don't know if sand would even be needed, I have luck here with Spanish Lavender. Unless the site you have is low and nothing but clay you shouldn't have too much trouble. I've found the Spanish type to be very easy to propagate too.

I've never had any luck planting lavender straight in the ground. My "soil" is pure red clay no matter how many amendments I've added over the years. They all seem to get eaten up never to be seen again. LOL!
A few years back, I got a variety of lavender called "Dilly Dilly" from Park Seed. I planted it in a sort of raised bed with mushroom compost, bagged garden soil (Miracle Gro or Scott's), and a bag of sand. (I couldn't remember which kind I used, hence my question. :) ) It's thrived and survived for 3-4 years now when all the other lavenders I've gotten from Lowe's/Home Depot didn't make it a season in pots. One even died planted in the same bed right next to the "Dilly Dilly"!
I got some Lavender Lady from the Bluestone Perennials 1/2 price sale earlier this summer and I'm hoping to duplicate my luck I had with the "Dilly Dilly". Might not succeed though since "Dilly Dilly" is an intermedia and "Lady" is an angustifolia. We'll see, I guess. :D