Mortar and Pestle: Granite vs Porcelain

Neither.

The traditional instrument for making guacamole, and other Mexican mashed and ground preparations, is the mocaljete, which is similar to a mortar & pestle, but made with a shorter pestle and out of black basalt, a rough volcanic stone:

A regular mortar and pestle out of ceramic or granite will not work for a fat, squishy fruit like avocado; it will just squish around and out of the bowl. You need the rough, pitted texture of the volcanic stone to "grab" the avocado pulp.

Personally, I find that the ideal tool for making guacamole or avocado salsas is actually a regular mixing bowl and a heavy pastry blender:

... but even a large metal serving fork will work fairly well. Better than a regular mortar and pestle will.

Porcelain or ceramic ones are:

• lighter

  You'll have to grab them with one hand to use them.

• easier to break

• cheaper

  ^{This is related with the last point.}

• glazed

  Porcelain ones don't need to be so, but ceramic ones are. It gives them a smoother surface, but some parts of the shell might husk off.

  It is not affected by acids (marble mortars will), and avoids the porcelain to absorb liquids (mostly oils, which will stay there forever). This is relevant for smashing avocados, as they are greasy and this kind of

Granite mortars are:

• unbreakable

  ^{Or very hard to break}

• heavier

  Harder to move from one place to other, but won't move off when you are using them. They also tend to have a wider base, so are more stable, for the same reason.

  This might be useful when emulsifying oils, as in mayonnaise or allioli, as you can have the pestle in one hand, and the oil you are pouring in the other one: you don't need to grab them due to their weight.

• coarser

  Having a rougher surface makes them more suitable for grinding finer or emulsifying oils.

• porous

  They'll absorb tastes and oils. You can't wash them with soap/detergent (as it will also be absorbed).

  It should be taken into consideration if planning to add them oils or greasy stuff like avocados.

When it comes to equipment, I consider Cook's Illustrated to be the Consumer Reports of cooking and refer to them. They recommend granite, or at least the one they recommend is granite. The Cilio (Frieling) Goliath. I'll refer you to their January 2012 edition to find their commentary about mortars and their full review (available at most libraries). You can read their commentary here: http://www.cooksillustrated.com/equipment/overview.asp?docid=36031

We bought one just last month but haven't used it yet.

Is a wooden one an option.

In have a deep olive wood morter and pestle, it is useless with anything hard like seeds, but for crushing soft veg and herbs it is really good.

It is easier to add harder ingredients first so I'd normally add garlic and a little olive oil before and crush before the avacado.