The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage.By David Gillie NEW YORK ( ETF Digest) --No matter what happens, basic materials are needed for the job. Whether it's flak jackets and gun powder for war, agriculture chemicals and pesticides for farming or coatings and ingredients for pharmaceuticals, basic materials are needed. Yes, even embalming chemicals and casket materials for death -- Materials Select Sector SPDR ( XLB) has it covered. Basic materials is the second derivative for nearly everything. We've recently seen a rally in the homebuilders. Although they may not be building house, they're building apartment buildings, converting condos and remodeling homes. All of this work requires copper for plumbing, paint for walls, adhesives for flooring, synthetics for counter tops and plastics for appliances. Biotech has also rallied. Pill coatings, capsule casings and compressed gasses and plastics are needed in the manufacturing of pharmaceuticals. Agriculture is showing signs of a new rally. Farmers are now scientists having to use the precise chemical blends in fertilizers and pesticides to maximize crop yields. If the economy is showing the first signs of growth, basic materials is in the first wave of a cyclical recovery. Further encouragement was the Fed announcement on Wednesday, which hinted at some relief in under-water mortgages and extended low interest rates through late 2014. The focus is a stimulus for the housing sector. This is good news for basic materials. Another factor of basic materials is that companies try to operate with existing materials in times of economic slowdown. Supplies dwindle to minimal inventories. At the first light of recovery, inventories must be replenished before the thick of the growth cycle, so they are on hand as needed. XLB holds the best of breed in basic materials producers.