What on earth is this and how do I eat it? 
http://www.florahealth.com/flora/home/canada/healthinformation/encyclopedias/Silicon.asp
Silicon is the second most abundant element of the earth’s crust (26%), second only to oxygen in abundance (49%). Silica, also known as silicon dioxide, is a compound made out of the two most abundant elements in the Earth’s crust, silicon and oxygen (SiO2). Silicon is not found free in nature but occurs chiefly as silica. Silicon is important to plant and animal life. Silicon was recognized as an essential trace element is 1972. In the human body, silicon is found in the connective tissues, tendons, ligaments, cartilage, and blood vessels and it is thought that the mineral is essential for their integrity. Silicon is also required for healthy nails, skin and hair and for calcium absorption in the early stages of bone formation. Studies have shown that the amount of silicon in arteries starts to decline as atherosclerosis starts to develop. French research suggests that silicon can help to prevent osteoporosis and can be used to treat bone fractures. Aging and low estrogen levels reputedly decrease the body’s ability to absorb silicon. A human fetus has an abundant supply of silicon in many tissues. Collagen, a primary component of connective tissue and a third of all body protein, is rich in silicon. Elastin is also rich in silicon. Silica, in close cooperation with vitamin C, has the ability of holding moisture in tissues through compounds known as mucopolysaccharides. Also known as glycosaminoglycanes, these mucilaginous carbohydrates together with collagen and elastin make up our connective tissues. Silica is also vital for tooth structures. It is involved in the hardening of enamel, prevents bleeding gums and recession (a cause of loose teeth) which ultimately can prevent the need for dentures. Horsetail is among the riches plant sources of silicon in the form of monosilicic acid, which the body can readily use.
Wow! Ok thanks.
Now the second part of the question
How do I eat it? Where do I get this Horsetail of which I never heard before? 
Is it eadible at least?
Are there any recipes? What other sources of vegetal silica exist?
Daily silica needs for humans are 20 - 30 mg.
natural foods that contain silica:
Food (100g) Silica Content (mg)
Corn 19.0
Parsley 13.0
Red Beets 21.0
Barley 233.0
Lettuce 6.0 - 7.0
Strawberries 6.0
Oats 595.0
Millet 500.0
Potatoes 200.0
Whole Wheat Grain 158.0
So you don’t have to eat horsetails
You can just eat whole oats