Another try

while true do
nolapis = false
lapis1 = turtle.getItemCount(5)
lapis2 = turtle.getItemCount(6)
lapis3 = turtle.getItemCount(9)
lapis4 = turtle.getItemCount(10)
if lapis1 < 2 then
nolapis = true
elseif lapis2 < 2 then
nolapis = true
elseif lapis3 < 2 then
nolapis = true
elseif lapis4 < 2 then
nolapis = true
end
if nolapis == true then
print("No lapis!")
sleep(1)
end
if nolapis == false then
print("Crafting diamond!")
if turtle.craft() == false then
turtle.select(16)
turtle.dropDown(16)
end
end
end