SPI Supplies Brand Agate Mortar and Pestle Set 60 mm x 50mm x 20 mm Deep Style

Advantages of an agate mortar and pestle set:

The number one purpose of any mortar and pestle set is to grind solids into fine powders but under conditions that are highly controlled as to not produce any heating effects and to minimize and control any effects due to stretching of sometimes deformable materials. This is probably the most ancient device one is likely to find in a modern scientific laboratory or kitchen. Because of the ability to control the grinding, and also to virtually eliminate contamination from the mortar and pestle set itself, agate is the preferred material and is used in laboratories and the finest kitchens worldwide to prepare delicate sauces and pastes and for the grinding of dried spices and herbs. From a cross-contamination and cleanliness (hygiene) standpoint if in the kitchen, the high density agate is far more desirable than the more porous porcelain which could grow bacteria in the pores and present a health problem. If a mortar and pestle of metal construction is used, it is generally recognized that metal particles enter the ground powder, thereby presenting either a health concern or else a contaminant is precision scientific measurements are to be made on the ground powder. 

A few words about "powdering" a sample:

The signal word is "purity" of the final powder. And when we use the term "purity" in this context, we mean, freedom from the impurities from the mortar and pestle set being used to powder up the sample. The amount of such impurities of course will be a function of the hardness of the material being powdered. 

While the SPI Supplies^® brand of porcelain mortar and pestle sets are of high quality so far as porcelain is concerned, agate is much harder and therefore, for any given hardness of material being powdered, there will be a definite lowering of the impurity levels from the mortar and pestle. 

Composition:

The mineral agate used for the SPI Supplies mortar and pestle sets is 99. 9% SiO₂ (in other words, quartz). It exhibits a Mohs Scratch Hardness of ~7 and this is what makes agate the ideal choice for tools for grinding or crushing even for the hardest of materials. Unlike porcelain, which is porous, the high quality agate used by SPI Supplies is high density (e.g. without porosity) which minimizes sample loss and reduces cross contamination between samples. For those who are geologically inclined, the specific agate used by SPI Supplies is of Brazilian origin which is recognized as being the hardest and most dense found anywhere in the world. So far as mortar and pestle sets are concerned, only zirconia mortars and pestles would be harder (e.g. Mohs Scratch Hardness of ~10 vs. ~7. The agate used by SPI Supplies is resistant to all solvents and acids except aqua regia and HF. 

Applications in the pharmaceutical industry:

Agate is the material of choice because of its hardness relative to the generally much less hard organic crystals and polymers being ground up. For sterilization of the agate mortar and pestles, we generally recommend an alcohol (or other chemical) type of sterilization as opposed to heat sterilization, which could damage the mortar. In general, if heat approaches must be taken, then we would suggest using a smaller rather than larger mortar and also, heating the mortar slowly instead of rapidly, to minimize the built up of internal stresses and eventually failure. 

Heating and cooling applications:

We know that some customers have needs to do the grinding either at elevated temperatures or at low (cryogenic) temperatures. Because of thermal expansion (or contraction) effects, we cannot guarantee the mortar and pestle sets against breakage when used under such conditions. 

A few words about the higher cost (relative to porcelain):

The SPI Supplies agate mortar and pestle sets are all precision hand crafted. However agate is a natural product and as the size desired becomes larger and larger, a stone of that size becomes more and more difficult to find, and therefore the cost escalates. For applications in the kitchen, the use of agate is much more "germ free" than when the much cheaper (and porous) porcelain is used.