high grade
Two types of stone were often used in building pyramids were granite and limestone.
See http://books.google.com/books?id=06s_8PnQIEcC&pg=PA18&lpg=PA18&dq=Cement+grade+limestone&source=bl&ots=E62c6KD0EV&sig=oxl0dtW_IwEidZw29ODE7f9K-tA&hl=en&ei=cI3gSoexIo2ssgPd-fHlCA&sa=X&oi=book_result&ct=result&resnum=10&ved=0CCIQ6AEwCTgK#
Low grade metamorphism occurs at lower temperatures and pressures, resulting in the formation of minerals like chlorite and serpentine. High grade metamorphism occurs at higher temperatures and pressures, leading to the formation of minerals like garnet and staurolite. Additionally, low grade metamorphism typically occurs in the shallower parts of the Earth's crust, while high grade metamorphism happens at deeper levels.
The levels of metamorphism are low-grade, medium-grade, and high-grade. These levels are based on the temperature, pressure, and chemical changes that rocks undergo during metamorphism. Low-grade metamorphism occurs at lower temperatures and pressures, while high-grade metamorphism occurs at higher temperatures and pressures.
Fairly low; most of the solar corona would be a high-grade vacuum.
High B or low A
High-grade rocks have a higher concentration of valuable minerals or elements, making them economically viable to mine. Low-grade rocks have a lower concentration of valuable minerals or elements, making extraction less economical and challenging. High-grade rocks typically yield a higher return on investment compared to low-grade rocks.
One or two places where minerals grow are high grade and low grade.
It's an ore that doesn't contain a very high proportion of valuable minerals. The term could also be applied to richer ores containing large amounts of undesirable impurities, arsenic for example. Low-grade ores are less valuable than higher-grade ones. Also, recovery rates for low grade ores tend to be lower than for high grade ores - that is, a lower percentage of the total amount of metal in the ore is extracted successfully. The definition of low-grade depends on the resource in question. For copper, low grade ores have less than 1% copper. For gold, an ore having 1% gold by mass would be considered (very) high-grade, as gold is more valuable than copper.
Low-grade energy: Based on the thermodynamic concepts, an energy source can be called as high-grade or low-grade, depending the ease with which it can be converted into other forms. Thus electrical energy is called a high-grade energy, as it is very easy to convert almost all of it into other energy forms such as thermal energy (say by using an electrical heater). Whereas, it is not possible to convert thermal energy completely into electrical energy (typical efficiencies of thermal power plants are around 30 percent), hence thermal energy is called a low-grade energy. Naturally, high-grade energy sources are more expensive compared to low-grade energy sources.
I am not sure if they are proportional, but they are inversely related. High pressure makes a low vacuum, and low pressure makes a high vacuum.