Processed to 4396 feet, slow drilling rock

Today we boxed rock core to a depth of 4396 ft, 79 ft deeper than yesterday.  Some of the lava units that we've been seeing lately are particularly rich in secondary zeolite minerals and smectite clays.  At least one of these secondary alteration products has a soapy, slippery consistency that is making it difficult for the drill bit to bite into and cut the rock.  Drilling units rich in this material can take two to three times as long as those without.  Here is a picture of a typical one of these units:

Note that the unit is also rich in olivine (brown from alteration, with a bit of green unaltered olivine visible in the center of some grains if you click on the photo and view the larger version).  The core is quite unfractured, implying that the secondary vesicle fill may actually be adding strength and coherency to the rock.  Not all the lava units look like this, but these type of units are encountered nearly every drilling shift at some point.